New 318 build, just need some input.

I think polishing will probably just slow it down a little bit. Gives it the effect of larger. flow more? maybe? How much? 2 cfm ,maybe more.. but probably not more than 10cfm.
It would be worth running those heads if your compression didn't end up really high for pump gas and you did the chamber mods and some mild bowl/short turn porting so that they flow as good as other open chamber heads, even better.
Otherwise why use that camshaft for heads that are designed and flow like truck heads? At the same time those heads were out they also had open chamber versions that went in cars... the trucks got the small chamber, the small chamber didn't allow the intake port to flow as well because it shrouds the valve. The open chamber heads allowed the intake port to flow a little better. what do trucks do? low speed torque. what do cars do? go down the highway in the fast lane light loads etc.
Sorry about the run-on sentence I'm using talk to text cuz I'm really really busy.
If you wanted something quick and easy and not aluminum heads...I would sell the 302s and get a fresh set of Magnum heads...then drill them for an LA intake OR simply use a aftermarket magnum 4 brl intake dual pattern knock off.
If you're going to do any work like polishing and stuff like that where you have to disassemble the head and clean it and all that mess.. you may as well put that work or effort into drilling for an LA bolt pattern on some better magnum heads with the same size chamber. You can then take your empty block and Bolt the heads onto it scribe them to the bores and then play with opening them up evenly to get to the chamber volume you need with those 167 Pistons so that you don't end up with two high compression for pump gas with that little idle to 5500 cam.

You asked.. that's just my opinion... if you don't like it..that's fine ...spare us both and don't bother responding to it in that case.
too busy.
Best of luck.