My 318 Build with questions

OK, well with the 4 valve reliefs the pistons could be either .080" or .100" below deck at TDC. If the OP could measure this carefully, he'll have better info.

Case 1 assuming:
- 8 cc total valve reliefs
- Standard Felpro gaskets
- 60 cc chambers
and -.100" deck height
CR is 7.7:1

Case 2 assuming
- 6 cc total valve reliefs
- Standard Felpro gaskets
- 58 cc chambers
and -.080" deck height
CR is 8.25:1

I am being pretty conservative above in estimating the chamber sizes (I think). It would help to do some more measurements (like cc'ing the heads and a precise the piston deck height measurement to see if it is .080" or .100") and perhaps plan on some more head shaving if you want to be up nearer to 9:1, and maybe some Felpro 1008 gaskets or even thinner ones. But at least the 256 cam will work well with no fear of too much compression ratio and consequent detonation. And with the low rear gears, more torque with less duration will be better IMHO. I might really consider some sort of stump-puller torque cam.... what do you plan to use this for? Pure street and cruising? Drag racing? The application will steer you a lot on what to do.

You are working to make the breathing better.... that will extend the RPM range of a milder cam. That is all real good. (I am channeling some 318willrun today....LOL) If you get the chance to extend the collectors, I'd do it for street use.