tryna get close to 400 hp...Wanna work out my 973 casting 318 heads

If I were you, I would find a set of Magnum heads and the gear that goes with it. Then have them milled for the desired compression ratio. Then go with a good sized cam with at least .500 lift and .230 duration at .050. Also hedders and a mopar m1 single plane for the rpm. Probably a 750 cfm carb too.

Edit, I noticed the cam you have listed. That's the one in my 318 and it sucks.. Not big enough.