Originally posted by bifflop
Any information or opinions on my idea would be appreciated
When you ask for opinions you're liable to get them, so here goes.

First off you didn't mention if your car is a two door or four door, sedan, hardtop, or wagon. But in general if it's a four door whatever money you spent on it would be a poor "investment". The market for tri-5's has been soft for almost two years now, relative to where it was, and may stay there for a while. Now usually the first thing someone says about this time is that they don't plan to sell the car. Well, planned or not, the odds are something like 999 to 1 you will, and mistakes now will cost you later (you've heard the pay me now, or pay me later thing right?).
Then the next thing they say is that two door models cost so much more. That's correct. That's because more people like and want them. It's called "market demand". When you realize that parts, materials, and labor/effort is going to cost the same for either body style, and that the typical four door will sell for about 1/4 the value of a two door when completed you see where the pay later comes from.

Also, your premise about the BBC being low availability really confuses me. I don't know the precise production figures, but if I had to guess I'd say that Chevrolet built at least 10 times as many big blocks as Caddy ever did of the 472/500, and that's probably real conservative. In fact, Chevrolet is STILL producing the BBC, but Caddy stopped the 472/500 a long time ago. Now if you're taking about core prices then yes, the BBC is more than the Cad. It's that demand thing again...................big message there. And if you were to do an unbiased comparison of modification parts for both engines the Cad would be more costly to build than the Chev. None of this is to say the Cad is a bad engine, just that your premise is wrong.

Lastly, putting a Cad engine in a tri-5 Chev is value suicide. Yeah, yeah, yeah, dare to be different. If tossing money away doesn't matter to you, go for it. It's been done before (so much for being "different") and look, it didn't start a trend. Unlike putting a small block Chev in an old Ford, which is now a 50 year old trend (might be catchin' on!), putting Cads in tri-5 Chevies is not popular. This too will kill the resale value of the car (pay me later).

Hope this helps.