Re: engine location in a 68
A BB will fit using all the SB stuff except that you will probably have clearance issues at the drivers side exhaust manifold or header and the steering gear box!
Right, try to buy NOS BB frame mounts and go. You can use the SB cross member by kicking the tranny tail-housing over about an inch and then use a three hole poly tranny mount using one bolt through the pass. side C/M hole and the center hole in the poly mount! That's the way my 496 BB is now and it fits fine!
Not stock, but fine!!
PS., and as stupid as this sounds, I wished I'd bought NOS 6-banger/early 350 rip-apart rubber mounts and used them instead of my poly mounts after drilling them and bolting them together using 45 degree countersink head, Grade-8 bolts and stuff to keep them from ripping apart b/c of AIR CLEANER HOOD CLEARANCE ISSUES!!
I say this only b/c those suckers are the thinnest there are and they will drop my engine down like maybe 3/8" to a 1/2" to gain the hood clearance I really need. I would just need to double check pan/cross member clearance and since I'm using a stock, 4 quart car/P/U oil pan, it should be fine. Remember it's actually 5 quarts w/ a quart in the filter back then..