Obviously, I am assuming custom size ones can be purchased.
I don't think so. I've never seen custom sized pilot bearings.

SBC (Gen I and Gen II) and LBC (MK IV, V, VI) pilot bearings are the same. I think the LS engines are the same, but can't verify.

http://store.summitracing.com/partde...ew=1&N=700+150+