I would if I had the money. It really sucks having a car like this that is slow.. :/

No reason that car should be slow, get in there and do some tuning, start with the distributer curve, makes a big differance.

Have you checked the timing?

Might be worth it to measure the cam if you don;t know what is in there. Maybe degree it. Could be retarded.

Thing is, that rebuild could have really sucked. Have any idea what is in there?

Take it for a drive with a vacuum gauge hooked up. At 65 on the highway that thing should be pulling at least 16-18 inches which should = 16-18 MPG give or take. It should also be idling with +20 inches if it has a stock type cam in it.
If optimizing the timing (vacuum advance is a MUST)and dialing in the carb ( I vote for the Thermoquad ) doesn't give you those numbers, I would look at how the cam is installed. If it DOES give those numbers at idle but not at cruise, I would look at swapping in the 3.23's. I used to have a 79 F100 with a 300 inline 6 that got 10 mpg on the highway and pulled about 10" of vacuum. Swapped in a set of 3.50's and the vacuum at the same speed was 16-18 and the mileage went up the same amount. Even tho it was buzzing 1000 rpm faster it wasn't working as hard. Food for thought.

Kevin