Anyone run a Street Avenger?

You have two problematic issues for street driving: Blocked heat, and mechanical secondaries with a tight converter. Either one will work, but as you have noticed, street manners will take a hit.

Your carb is certainly not too big. The stock Thermoquad on your 71 was 750+ CFM. For mostly street I'd suggest a 750 Edelbrock AFB or AVS. Street/strip and I'd run an old school Holley 3310.

I would be concerned with the "constant fiddling" however. It should be repeatable once warm with the setup you have. You should not have to monkey with it once set. You will probably be able to make it run well when warm, run OK cold or get decent gas mileage. I doubt you'll get all three with that setup. BUT once set, it should not change by itself!!

If you tune up is always changing, look beyond the carb. An old saying is "99% of carb problems are in the distributor". My experience says this saying holds true, and in many cases so long as you have a good timely spark any carb which is fairly close will run pretty darn good.

What is your ignition setup? Intake/exhaust?