Here are some examples I dug up:
Engine www.jasperengines.com
1975 Jasper 5.9L V8 (Carbed): $2000
Transmission www.jasperengines.com
1975 Jasper A727 (Auto) $1105
(Though the trans Bob has may be good enough.)
Rear End
Slant 6 diffs were pretty stout, slip in a set of gears and he'd be good to go with the power a 1975 5.9 would put out. (Around 250hp stock.)
Swap Kit
Schumacher Creative Services
http://www.engine-swaps.com/ sells a swap kit that would allow Bob to go from his slant 6 to a V8 without using a new crossmember for around $200.
So, that is about $3,500 for all new parts. Of course he could go the junk yard route. Buy an emgine and have it rebuilt etc, it would be a lot cheaper that way, although he would still need to get the swap kit.
[ December 20, 2001: Message edited by: LHSer ]