318 with 360 heads and compcam build help

Sounds like you're committed to the 318. You do your project however you want. You're getting some good advice here. something that I don't think has been brought up is this, engine projects take time and they can suffer from mission creep. This can make the project take longer than you may plan on.

Sounds like you have a running drivable 318. You could have that motor in and be able to drive and enjoy your car while you build your replacement motor. You have a 360 block and 360 heads. If you are planning on boring the 318 and replacing the pistons you could do the same to the 360 at the same cost. You would need to come up with a crankshaft and rods. They could be found from someone doing a stroker or elsewhere.

I'm not against a 318 but if you looking for extra power with out sacrificing driveability it's hard to beat cubic inches. And you already have the parts for a 360 based build.

When your replacement motor is done your downtime will just be a motor swap instead of a motor build and swap. And until it's done you get to drive and enjoy your car which might help keep you motivated. Good luck with your project.