My tach weirdly stopped working so I'll have to get that up and running again to answer the rpm question but as I remember, I do think it was about 2200@65.
Well then, start working on the timing. Rusty has been asking, and me too,
However if that 340 has a factory cam, then 17 is pretty good. That cam was terrible for fuel economy.
I can tell you how to set your cruise-timing, but that doesn't mean that you will automatically get any better than the 17 mpg that you are now getting, and in the process, it might mess up your power-timing, and or PT timing.
Just make sure you have a working Vacuum advance system.
Part of the problem is that with the factory cam, 2200 is almost too slow to run a 340. Another is that the power stroke is very short.
Another is that most everybody recommends to run that cam advanced, which just aggravates things.
As far as cams go, the factory 340 cam, being on a 114 LSA is just too far apart. this chews up compression degrees all rightee to help keep it out of detonation, but it also chews up power stroke, which leaves a lot of cylinder pressure escaping into the exhaust, which could have been sent to the crank, to power the vehicle down the hiway. Instead it just puffs out the tailpipes.
Everybody used to rave about that cam, but not me. IMO, it was a terrible street cam. I mean I kindof understand why that cam got in there, but back in the day, it was one of the first things to get rid of, right after installing headers.. Today we have many better designs. IIRC I got 4 or 5 boxed up around here somewhere.
But you know, 1972 was a long time ago, and chances are that the original cam is long gone.... and who really knows what cam is in it...............
