if you go with the mag heads, you can get a crosswinds intake that will fit both the LA head or the Magnum..

Heres what i would do.. 318+magnum heads+crosswinds intake, comp cam xe262 or 268H, a 650 carb, headers, a TC to mach the cam, and new lifters, and proper legnth pushrods and matching Valve springs, timing chain with a tensioner.

you can get re-man mag heads from CMengines.com or new ones from engine quest.

or if u wanna go cheap, 318+used 360heads milled a bunch, then you may need the intake serface milled as well. .028 head gasket, try to get a least 9.0 CR (talk to your shop) a 360 4 brrl TQ intake,or a rpm airgap or a crosswinds intake, a xe262 cam or a repo 340 stick shift cam and new lifters and springs, 360 exhuast manifolds or headers.

I did this on a 68 318, the pistons on the 68 were flat tops with 4 valve reliefs. I think yours will be different.

next one i do will be a LA magnum hybrid

http://www.popularhotrodding.com/enginemasters/articles/mopar/0667em_mopar_318_engine/index.html