360 heads suck on a 318! any power gain from the bigger ports is lost due to what it does to the compression and crevice volume. The factory did it to reduce NOX emissions and as a result the 4bbl motors only make a few more hp than the 2bbls. If you are gonna do the 360 heads you need to do something drastic to increase compression. 300 hp is not hard to do with any 318 heads, the 920 is the best small port head for hp, the 302 is best for MPG.