I am posting an incredibly informative reply I got from a headlight guru. I thought it was good reference material.
My headlamps don't provide enough light on low beam for safe driving at night, so I am going to upgrade them. I am not advertising for this guy, but he may be a great resource if you decide to undertake a project like this. I will post later on my outcome.
The email:
Those are indeed '87-'91 Ford F-series truck headlamps. They use the 9004
> bulb and optical system. The 9004 system itself is optical trash. This
> was Ford's "Better Idea" (remember that ad campaign?) for 1983, and the
> design priorities were cosmetics (aero headlamps instead of sealed beams)
> and low production cost. 9004 headlamps, even with the least-bad bulbs fed
> by proper wiring, will always produce dim, poorly-focused, narrow beams
> with very little light on the road surface and very high levels of upward
> stray light that cause backdazzle in rain, fog, and snow.
>
> There are no well-made overwattage 9004 bulbs, only poorly-made ones from
> the 3rd world, with very sloppy filament placement. Tiny differences in
> filament placement make huge differences in beam focus and performance,
> see attached. The extra light some of these higher-wattage bulbs produce
> is pretty much all wasted: Extra glare and flare light, no extra seeing
> light. And, the stock wiring is inadequate for the extra current drawn by
> these bulbs; using them throws a severe strain on the wiring and switches.
> In most(!) cases you won't have a big spectacular fire or anything, but
> you won't be doing your electrical system any favors, and the damage is
> cumulative to the point of expensive failure. Overwattage 9004 bulbs are
> NOT the way to better seeing.
>
> If you are just trying to make the existing lamps marginally less dim, you
> can put in a relay kit RIK-HB1 and a pair of the least-worst-available
> 9004 bulbs. Those are the GE Night Hawk 9004NH and the Philips VisionPlus
> 9004VP. I don't presently stock either bulb, but a web search should turn
> up a retailer for you. Avoid Sylvania Silverstar/Ultra, Wagner TruView,
> PIAA, Hoen, and all other brands of blue-glass "extra white" or "xenon
> matching" bulbs. They are a scam; despite the advertising hype, they
> significantly reduce headlamp performance rather than increasing it.
>
> If you're trying for a material safety performance improvement via
> significantly better seeing with wider and longer beam reach and reduced
> backglare in bad weather, we will need to look at better-engineered
> headlamp assemblies.
>
> On the internet, you'll find a pile of suggested modifications and
> "upgrades" that are mostly ignorant and ill-advised. Changing to a 9007
> bulb in a headlamp designed for 9004 bulbs makes things considerably
> worse, not better, because now not only have you got a very
> poorly-designed optical system, but you've got a bulb other than what the
> optics are designed for. Kind of like putting somebody else's eyeglasses
> on...they might look OK on your face, but you won't see properly. This
> bulb swap results in greatly increased glare to other road users and
> backscatter in rain, fog, or snow. Please don't do it. And "HID kits" are
> unsafe and illegal, see
>
Daniel Stern Lighting Consultancy and Supply
>
> Now...how to do it all right? Well, there's some money that needs
> spending, and a bit of a wait for special-order lamps to come in, but the
> fact is, there are very well made glass-and-metal headlamps available to
> fit your RV. They were factory installed on '87-'91 Ford F-series trucks
> originally sold in export markets with headlamp standards significantly
> more stringent than the US standards. Low and high beam are considerably
> better focused. Low beam is much wider, more even, and longer-reaching,
> while at the same time there's much less glare to other drivers and the
> backdazzle in rain, fog, and snow is totally eliminated. High beam is wide
> and even with considerably greater distance reach. And because the lenses
> are glass, they will never cloud-up and turn yellow like the original
> plastic lenses. Anti-rock guard material is available to prevent the lamps
> cracking or getting sandblasted. A relay kit will be called for, to bring
> full power to the lamps -- see
>
Daniel Stern Lighting Consultancy and Supply -- and if you
> want a daytime running light function, that's doable, too.
>
> As I say, these are special-order lamps. They cost around $156/ea. I do
> have one left-side lamp on the shelf from a factory mixup the last time we
> ordered in a set of these (factory sent two lefts instead of a right and a
> left).
>
> If I were trying to set up a vehicle like yours for really good nighttime
> seeing, I'd replace all four of those cheesy plastic Ford headlights with
> the good glass and metal units. I'd put in a relay package RIK-H4R4, $66.
> The RIK is not a harness, but a _parts kit_ containing all relays,
> brackets, terminal blocks, terminals, plugs, sockets, fuses and
> fuseholders. You supply your own wire and use the parts from the kit to
> build up your own wiring harness. Parts are specially made premium-grade
> items (e.g. ceramic headlamp sockets) that accept large-gauge wire; this
> is not the "consumer grade" junk you can find at the parts store. You will
> need to run some new wires, but you will _not_ need not cut or otherwise
> disturb any of the vehicle's original wires.
>
> There are various good options for bulb selection. I would probably not
> run the same bulbs in all four lamps. In the outboard units, I'd run Osram
> ultra high efficacy bulbs, either 70/65w or 85/80w. In the inboard units,
> I'd run Narva 100/55w bulbs with re-usable selective-yellow clip-on
> balloons. All four high beams would come on when you select the high beam
> mode. I'd probably put a switch in the line to the inboard low beams; they
> would serve as vastly more effective fog lamps than you have now (assuming
> you have any right now). Of course, all four lamps would need to be
> carefully and correctly aimed, per
>
Daniel Stern Lighting Consultancy and Supply .
>
> If you are interested in having a daytime running light function on your
> vehicle, the best implementation is the full-time operation of the front
> directional signals (except, of course, when they are operating as signals).
> Directional signals produce a light distribution with a wide conspicuity
> angle, are generally well located for DRL service at the outboard edges of
> the front of the vehicle, consume considerably less power than any
> headlamp-based DRL implementation, use light sources of generally much
> longer life than any headlamp bulb, do not encourage improper nighttime use
> of lights, and do not require additional lighting devices to be added. Most
> recent Cadillacs, Chevrolet/GMC large vans and minivans, some Toyota and
> Lexus models, certain new Lincolns and assorted other vehicles use this
> implementation. Note we are talking about the full-time operation of the
> bright amber turn signals, not the dim parking lamps. You can easily enable
> this functionality in your vehicle using a DRL-1 module ($42 here, see
>
DRL-1 Daytime Running Lamp Module Installation )
>
> So...give this all some thought, and come back with whatever questions you
> might have.
>
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