MagnumMPI swap - crank pickup fix?

He says 21.2 with 3.23 and BFG 295/50/15's. Likely a bit more with that big a tire.
This summer he swapped in an aluminum OD, and his mileage dropped to 20ish.
but with the 3.23's his rpm is so low at 55-60 that the engine is really lugging.
It's really great around 80 tho.
He just got a set of 3.91s for next year.

Its a bone stock engine with only a set of headers.

Thanks!

Is it pretty fast?