You will get a better response posting in the Hotrodding Basics forum instead of the Intro forum.
Anyway, when we say "Vortec" heads, we're talking about the casting number 906 or 062 heads from 1996-2000 (until '02 in selected applications) L31 5.7L engines used in trucks and SUV's. A LOT of info on Vortec heads and mods to them, etc. is HERE.
The two castings that Cobalt refrenced above will not take a cam over .420 lift(GM says .440) without modifying either the way they are sealed from oil or maching down the valve spring locators that are cast in the head. If you do neither and run a higher lift cam the bottom of the spring retainer will hit the top of the valve stem seal when using stock replacement valve stem seals.
I just had to do this on a guys truck. 906 casting heads, .503 lift. Luckily the valves in the heads were older style so I put oil skirts and o- ring style seals on each valve and it was good. The best solution since you don't appear to have anything picked out/assembled is to have the locators cut down for extra room.
The L31 heads will be too small in the intake runners for a stroker motor. The motor will run fine, but you'll be down 100 hp by using them on a stroker motor over the power the motor will make with bigger heads.
I wouldn't use L31's on anything bigger than a 350 unless I specifically wanted to make a low-rpm torque motor that would begin signing off at 4500 rpm's.
You can get away with more static compression ratio using aluminum heads, but I'd be thinkin' about a 9.5:1 limit with iron heads. Match the camshaft accordingly.
There are literally dozens if not hundreds of builds/dyno tests of 383 SBC engines using Vortec heads. Just do a search...
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