Personally? I'd stash the original numbers engine (or just the bare block) get another similar engine to build (you didn't mention what it is?) assuming it's a 383 you can get another one, or a 400 which looks the same externally, and build it for fun with a stroker kit, etc. and have a bunch more power/fun.
Shouldn't cost a ton more than rebuilding a stock engine with what's available off the shelf today. This way you can have fun beating on it and not worry about damaging the cars numbers matching status.
.02
Why not to stroke the stock engine from 383 to 426 ? it won't harm the block, original crank can be storaged, is just about upgrade the rotation assembly ( crank and pistons ), and just if whished, one step up camshaft to enjoy the power sensation without loose the driver comfort on street
just my .02 :P
AN if not...
Why not simply rebuild the engine with KB pistons?. They are higher than stock ones so will raise the compresssion a bit. Keep the Magnum camshaft or replace it for something just a bit hotter and done! its time to do it as any other job after all these years. It hasn't to be something to worry or a headache.
