Half the depth on the nut... Do you mean flange(ed) nuts?
As far as a supplier the choices are vast.
keep in mind the tensile, shear and bending strength of your replacement hardware, be it stainless, Grade(s)3,5,8, etc., or hopeful unknown from your tenyear box. That part of the suspension (if I've read your post right) takes a beating and no second-string bolt will do.
How many Harleys have been put to the side-o-the-road on account of 2nd rate hardware, including wiring ect ?
My favorite go-to for hardware, rod-ends, wiring, clamps, etc. is MIL Spec or aircraft. A little bit more patience to find, and a coup'la dollars more to acquire...... but oh! the long-term rewards when (if) you keep at it (depending on how long you plan to keep the bike. Most of the threads on a/c screws and especially bolts, are rolled, not cut threads; a 5-10X eye loupe will often show the difference.
I rely on a little book called The Aircraft Standards Handbook; a huge mine of old/new Harley-relevant information between two small wire-bound covers. Cheap on t'bay. Speaking of cheap, I just picked up 20-5/16 mil.spec., unf, high-temp silver-plated locknuts (these for rocker boxes); less thana buck each, so just cause it be a/c don't mean it's irrationally expensive
I'm building one and re-building 2 FX's, all at once. As one, they will be drenched in mil.spec. a/c hardware wherever possible; this is so only because I have plans to never sell any of them. Your purposes will vary from mine I reckon.
