318 t/b swap onto 360 carbed

Drop to a 600 CFM vacuum seconday carb and you will help torque and maybe gain a mile or 2 in mileage.
As you stand right now I'd say you aren't going to get a lot more mileage out of it, but I could be wrong.

What gears are you running? A 360 can handle 2.76s in an A body without lugging it.

Mark.