Hi,
I would start with a fresh rotating assembly. The old crank/rod stuff was way heavier than the '82 and up 5 liter stuff,this alone revs faster and makes more power. You need new pistons anyway,there is no way to get 10:1 out of your 12:1 pistons.
The best way to get your 400 hp out of a small block is with a 347 stroker kit,less radical cam also.
Good Luck,
Perry.
