i replace mine through grainger as well.
mine was Gast model number 3HBB-32-M300X, grainger part number was
2Z868. that was an exact replacement. i also kept my old one but never got around to rebuilding it.
in 2008 i paid $437 plus tax, so they are pricey. they are industrial grade.
unfortunately, grainger lists them currently as discontinued.
if you go to
www.grainger.com and put in their part number, it will say discontinued and there is a link to alternative models. it shows the other 1/3 hp 100psi models with similar cfm. pay attention to the sound levels in db. i was going for quiet.
they used to carry rebuild kits for ours, so you might check with them.
they are closer to $600 now and different dimensions.
nothing is cheap on our babies.
tom