FWIW. Post 13-16 by BBMopar Memike ff6 67Dart273 are giving you good advice for tuning. A dash mounted vac gage is a decent low buck alternative to Wideband O2 (AFR) gage or logger. Yup. You need to go to Eddy's website and download the tuning manuals. Jetting effects higher rpm and load but you'll need to tune idle and transition for milage gains at 50 mph and below. A spreadbore gets on the mains a little earlier.
I disagree with your assumption that the timing is 'dead on'. If you had a factory cam, a factory dizzy, and set the initial to the factory specs, then it would be dead on. But you don't have any of those. at best you are ballpark. There's also a caveat as emmissions got more important, the factory sometimes compromised milage to keep NOx down. If you de-EGRed the car, then for best milage you may want to use an earlier year as a baseline. If it didn't have EGR, or you kept the EGR, then '74 is probably OK.
In any event, tuning is iterative. After checking engine condition, measure the timing curves, check the spark plug conditions, and then make your changes - one at a time. Carb then timing, timing then carb, whatever, just have a plan and do one change at a time. Vacuum and AFR gages (with rpm) will provide some immediate feedback. They won't tell you if it can pull a load. That you have to judge while driving.
I disagree with your assumption that the timing is 'dead on'. If you had a factory cam, a factory dizzy, and set the initial to the factory specs, then it would be dead on. But you don't have any of those. at best you are ballpark. There's also a caveat as emmissions got more important, the factory sometimes compromised milage to keep NOx down. If you de-EGRed the car, then for best milage you may want to use an earlier year as a baseline. If it didn't have EGR, or you kept the EGR, then '74 is probably OK.
In any event, tuning is iterative. After checking engine condition, measure the timing curves, check the spark plug conditions, and then make your changes - one at a time. Carb then timing, timing then carb, whatever, just have a plan and do one change at a time. Vacuum and AFR gages (with rpm) will provide some immediate feedback. They won't tell you if it can pull a load. That you have to judge while driving.