Go for it. A few things the 318 heads lack but can be overcome with work and $$$'s is small valves and small ports. The 340/360 heads have bigger of both when teemed with a good intake, 4 barrel. decent sized cam, headers and the like will produce good power. The cam will tell you when (RPM) . Thinking in a compression direction, a close to zero deck 318 with the closed chambered 920 heads can make more power as well but not as much as the big valve/big port heads do. This combination is better for a mild street engine where big HP/RPM numbers aren't wanted.