Find a 91 or 92 Dakota with a 318 and grab the heads off that.
They are closed chamber to raise comp ratio and have the positive valve seals too. You can use ALL you stock valve train if you want. The valves are the same size as 360 's.
I have a set on MY 360 (yeah thats right) 318 heads on a 360..I beat my buddies Hemi pick-up with the old Dart. So you can judge from that. I don't know what the stock Hemi's do in the 1/4 mile,but, I don't need one.

I bought 9.5 Kieth Black pistons for stock heads but With the closed chamber Heads I think I am a little over 9.5 to 1.