How to identify "302" heads???

How much power you looking for ?
stock 318 heads are good for about 300 hp.

If you built a pocket ported 302 heads with 9.5:1 cr with quench be nice and a something like a comp xe268h-xe275h cam might do a 323 cid @ 323 hp engine, If you want more than that you need better heads and or more cam & CR. Personally I'd go with at least Magnum or even 360LA heads if you added cr with pistons.