360 build
For this build, I wouldnt put seats in it. With the 340/360 chambers and the short as built, you will have a true compression around 7.5:1. Use the MP thin head gaskets or it will be less than that. On the up side, piston to valve clearance is pretty good even with no valve reliefs. Have a valve job done and have the intake valves back cut as part of the valve job. It's a little extra $$ but will help out flow without touching the ports. I agree with what was said... dont port them.