Ok so I'm build a 318 stock bore flat top pistons new bottom end either a 454 lift cam or a 480 lift summit grind 4 speed is putting 360 J heads on it going to help it or hurt it
The it from a “Been there and done it” guy (myself) for the last 40 years, OK?
Look towards a piston like a KB and have the piston set at a zero deck height. For a 350 head, the letter heads have an open chamber which require milling for a reasonable compression ratio. Look for a later 360 head with a closed chamber or to a aluminum head with a closed chamber and have it bowl ported with short side radius work done for best low lift flow from the head.
You’re shooting for a 10-1 to a 10.5-1 ratio max. 11-1 with an aluminum head is fine for 93 octane. If only 91 octane is available, drop the compression ratio by a 1/2 point.
If your cylinder heads have a 1.88 intake valve, have a cam LSA of 198. If your cylinder heads have a 2.02 valve, use a 110 LSA, which most off the shelf cams are ground with.