Sounds like you have a stash of good parts sitting there so for you it wouldn't make any sense.
The argument that they're prohibitively expensive gets holes poked in it pretty fast though. Rocker Arms are expensive, but a good set of quality rockers for a SB or BB aren't far behind. You can get a good intake now for $500. Cam, last I looked a roller cam set for a SB or BB was $800, in line for what you pay for a Gen III (although all you need is a cam ($400 ish), factory lifters are good for 7K and you can convert them to solids). Rotating assemblies are a wash. Where you get some $$$ back is you can walk into a junkyard and leave with a cross bolted 800+ hp capable block (reliably) and heads that flow 300+ before porting (Eagles), to get those capabilities with a SB or BB you need to look at the aftermarket. Yes you can't buy $89 Summit Racing flat tappet cams but that's not the type of build you're looking at.
