need advise in a 318

Depending on how much it costs to clean up a set of 302 heads, oversize valves and good springs you might want to look at RHS or Iron Ram heads by hughesengines.com depending on what your'e shooting for newer heads might be better. 5sps might be able to find one from a dakota or half ton. Look for a NV3500, the heavy duty version has a low 4:1 first gear, the id tag is stamped on the left hand side, there is a light duty version as well. Good luck and have fun