318 head porting for the average joe

As far as getting smaller chambers on a 360 head I don't want to have to shave enough off to introduce manifold sealing and fitment issues. At one point I had 2 ex squad diplomats. One 2 bbl the other a 4 bbl engine. I never had the heads off of either but the 2 bbl one had the 302 heads, the 4 bbl one had "360" heads, as it had "360" cast into the heads (besides the casting number which was elsewhere on the head) both had 904s (probably actually the 998 version of the 904, being mid 80s cars) and both had 2.94 gears. The 2 bbl one ran better than the 4 bbl one, it would run circles around the 4 bbl car. Even my 87 3/4 ton van, also a 2 bbl 318 with 302 heads, would outrun the 89 (the diplomat that had the 4 bbl) and strangely the van also had the same 2.94 gearing.