There are many good benefits using A-heads.
Engine runs cooler.
Saves wieght.
More power.
Can use 87-9 octane with 10.5 c.r. depending on camshaft.

Will have to use hedders or RAIV/455 H.O.-S.D. manifolds.
Then theres recalibrating the carb and distributor.

Edelbrock's have a 5/8's thick deck surface.
They wont warp very easy.
1.800 installed valve hieght good for .575 lift(i would stay under .550)
Should use at least a RAIV cam.

No matter who's you buy, be sure you dissasemble and check'm before intalling.
Sometimes there's some crud left in them, or a valve seat's may not be fully finished, etc.