318 Build - Expert Review Needed

you can re-drill the mag heads or again, sell and buy mag intake. Just saying the heads seems to be topic of bottleneck, magnums are a fast, cheap way to fix it instead of installing bigger valves (buying valves, buying seats, paying somebody to do the work) and porting.
Just more work. at the machine shop. A big horsepower build is not necessary here:

This is a street car that will never see a track.