Aluminum headed 318s?

I assume your looking at edelbrock heads.
Non ported ones will produce 450 ish hp.

The main thing you got to remember when building a 318 over a 360 is that it's gonna need more gear and stall and the powerband is also gonna be moved up about 600 rpms or so.

So a 450 hp 318 will make peak power around 6500 rpm and peak torque around 5000 rpms. And be pretty weak under 2500 rpm where most cars doing 90% of there driving so gears are very important to make a 318 work I wouldn't go under 3.91.