big blocks suck gas for sure, and if you want it for the highway, an OD is the only way to go, I figure I'll be lucky if
the 454 in my bus will get 8-10 taking it easy with a 4L80 trans [easy fit for a 454]
and the 2 speed axle won't help much, you have a 7.20 with the single speed, and the 2 speed is 6.40 at best, 8.72 otherwise
Bill
