If the goal is a good performing engine that's easy on fuel it may be worth keeping in mind many things that improve performance or HP per cubic inch will also increase efficiency or reduce BSFC. I'm not sure what factory compression ratio is on these, but higher compression gives greater efficiency. Volumetric efficiency can be improved with head porting, intake, carb, exhaust. Not sure the specs on the original cams but something with more lift and more aggressive lobe profiles while maintaining a wide LSA can improve efficiency as well. Polishing chambers can help to prevent detonation and helps to run the most ideal timing curve.

What pistons are you using? What is the compression ratio? Have you picked a cam yet? What octane fuel are you planning to run?

I enjoy engine builds and have done a few torque and efficiency builds. I like shooting for best fuel economy in builds like this. Even for a low cost stockish rebuild there's a lot that can be done for minimal cost to improve on both power and economy.