Love my new engine/trans;hate the MPG!

[68Gold/white]

I think there's tuning to be done here, before buying ANYTHING! Not trying to sound like a Beavis here...
From what I can tell the rear gear is still unknown...the common 350/350 gear was a 3.07.
Every engine is different. some won't due well lugging at lower RPM's, many have voiced this, I agree.
Do you know what your total timing is???

What type of distributor is it??? Does it have vacuum advance? Is the vacuum advance hooked up???

You must have dished pistons, with 64 cc heads on a 383. Your timing will need to be carefully dialed in with this combo, not even considering the MPG situation...