FORGET CHANGING THE HEADS!

I figured out a rebuild for my friend's '75 440 3/4 ton 4x4. It went like this:
KB 184 pistons with stock heads.
Hughes hydraulic camshaft closest thing now is SEH1620BL-12
Headers
Stock Thermoquad
I cant remember whether it used a Performer or a stock intake.

Horsepower and fuel economy doubled, from 7 to 15mpg. Truck now had some zip. He was extremely happy. The expense and aggravation were worth the money.

Your stock pistons are so far down, probably 0.180"(7.1:1 compression), that taking 16 cc out of the heads would net you still only 8.5:1 and you'd still have the open detonation prone chamber because no squish from the piston. They've got to go.

The 184s will get you 9:1 and have squish. Attention will have to be paid for clearance between top of "quench dome" and cylinder head. Some scaremongers will try to frighten you but it usually works out pretty close.

R.