well fuel milage is my last concern.i so want to jam a cummins under this cab it aint funny.but then again the 348 is a pretty rare engine even in the cars.so would love to keep it and maybe put a 700r4 behind it as i happen to have one from an 84 pickup.should help a little on milage.or maybe an nv4500 beings it is a manual AND i happen to have one of those laying around.