Can I make this work on pump gas?

You may want to, but if I were you, no matter which head and gasket combo used, I would put it through a valve clearance test off of a solid or shimmed/ locked hydraulic, with some light springs on the #1 intake and exhaust. 1st and 3rd lobe of the cam from the front.

You're looking for clearances from the crank sweep starting at 15btdc to 5btdc and again from 5atdc to 15atdc.

You want .100" clearance between the valve and piston on the exhaust of over extending the rocker by hand until it touches, and .060" on the intake, min.

You may want to just set up some 308s or some J heads. 915s will get you there. Any stock J head with some dished valves should put you at around 71cc. If you tossed some of those Fel-pro gaskets on it that got you about .053" crush, you'd be within your range.

Another thing you may consider doing is polishing the chambers, if you're up for it. Get more CC and better detonation resistance at the same time, since you're not going for quench.

Another option that I haven't heard mentioned on the cheap is water injection.

E-85 does kill aluminum, but not for a long time. About the only thing that gets hammered by that stuff that I've actually seen in shorter time frames than longer are things like metering blocks. Most new carb bodies are set up for ethanol and have nickel plating or another coating inside the fuel bowls.

If you want to have the convenience of pump gas, you may consider rigging a water injection system to WOT or check throttle position on ping and set up a switch at that level.

If I were going after it, I'd try the Fel-Pro gaskets without spending tons on the Cometics, then cut and polish the crap out of those X head chambers. Maybe get some open faced valves and shoot for 71-72cc.