5.2 magnum A833 2.93 Highway MPG

a small carb doesn't always equate to MPG, although it can help, especially in city driving.

by the maths your 26.5" tire with 2.94 gears should have you turning 2500 at 67mph which would be fine if you're soft pedaling it and in the #2 lane.

the trick here is going to be dialing in your timing so that you have enough at your projected cruise speed/rpm to make it efficient and work well, but not suck everywhere else.

if your cam specs don't favor your projected cruise speed & rpm then even an SP2 and 390cfm carb won't pull the mpgs you're looking for-- even if you drive like a grandma.

but set up right? i could see 20's on the highway if you keep it to a dull roar, but the street is gonna eat you up and keep it low teens.