Did you install a windage tray? With the tray and 2 gaskets, you may gain close to 1/8th inch more clearance.
If you cut the studs, keep in mind you need at least 1.5 threads out past the top of the nut.
Please don't take offense, but could it be the
oil you see is coming from the rear main seal or around the rear main cap? Those can be tricky to get sealed correctly....."nails...what a crude way way to ensure a seal.
If you do get regular FE bolts, I see nothing wrong with used ones. Thes arn't like modern engines which use a lot of "torque-to-yield" bolts that can only be used once.
I wouldn't be against using brand name grade 8 bolts if I couldn't find anything else.