timing a 318 w/a 495 lift cam!!!!!

Unless you shaved those heads significantly, your static compression ratio is pretty low and that cam will bleed off low RPM cylinder pressure quite a bit. Therefore, to try to gain back some low end I would think you would want to run a pretty good amount of initial advance, and light springs in your distributor. Max advance should be held to 36 degrees or you may have detonation issues at higher RPM.

An old trick to get it "close" would be to advance timing at idle to the highest RPM and then back it down 10 degrees