May I suggest:
1. 5 or 6 speed transmission.
2. 2.73 rear gear ( Last I checked, the 8.8 had a 2.73 )
I had a toploaded with a Boss 351, 4 miles to the gallon. Did a good amount of engine work, took out the toploader and put in a 5 speed with OD. Took the 4.56 gear out and put in a 3.5.
Went from 4 miles to 18 miles.
