Hey Russ, look at these:
http://www.readybrake.com/accessories.html
At the bottom of the page, they have 8000# rating. I had to use the straight extension when I added the readybrake (lever would hit the fiberglass when braking) and found that most other brands had a 5000# rating. Very well made.
Give them a call and they should be able to help with your questions.
I also used grade 8 bolts instead of a pin.