Engine rebuild question

I can offer one suggestion for your consideration. My experience is with Chrysler engines of that era in motorhomes. The "personality" of an engine can be changed by changing valve timing, meaning advancing or retarding the camshaft. Today we get the best of both worlds with complicated "variable valve timing systems. For Chrysler engines, there is a square key between the camshaft and its sprocket. They offered a key that looked like it had sheared part way, that when installed, moved the camshaft two degrees. You could install it either way to advance valve timing two degrees, or the other way to retard it two degrees. On GM and similar engine designs, they used a round dowel pin. You could buy sprockets with three holes for that pin instead of the normal "one". Using one hole retarded valve timing. Using the other hole advanced it.

Changing valve timing adjusts where more power and torque is developed. The way I remember it is "L" is for a "loose" timing chain which would make the camshaft "late", resulting in greatly increased torque at the low end. Great for motorhomes trying to pull away from a stop sign, but useless for passing at highway speed without a long head start. "T" is for a "tight" timing chain, resulting in greatly increased "top" end torque, due to the camshaft being "advanced". Uhm, "T" for "advanced". I had a 440 c.I. In an old police car that went from 0 to 60 mph like any old 318, but once on the highway, from 0 to 90 it tore the seats off its hinges! Its personality was meant for high-speed pursuit. Race engines are built the same way with little regard to how much power they develop at low speeds.

I also built a 318 with a "gas mileage camshaft". Turns out it was the same camshaft they used in motorhomes. My old station wagon could squeal the tires all over the place, but with steady highway driving, it got much better fuel mileage than the original engine delivered, and still had plenty of power for passing. I'm not an expert at interpreting all of the numbers related to camshaft lift and duration, but for what you're trying to do, I'd start with valve timing. It puts the power band closer to where you want it rather than using other modifications that increase power overall, along with increased fuel consumption. Mostly that has to do with increasing compression ratio. Things like that give you benefits you don't need and will cost in some other way, like fuel mileage.

I'd invite some of our other experts to add their comments of value too.