The second major Jeep engine, the F4-134 made some improvements to overall compression, and therefore a slight improvement to power output.
The "F-head" differs from the "L-head" engine in that the exhaust valves are still in the engine block, but the intake valves are now in the cylinder head - which improved engine breathing, and therefore volumetric efficency. This also accounts for the slight increase in power over the L4-134 used by Willys.
I haven't found much on this engine yet, but it also went out of use in the 1960's - so give me a little time to dig...