Thanks guys. At 2400 rpm, which is at it's torque peak, with the 3.54 I should be able to cruise at about 60mph, with the 3.07 it'd be about 67mph. Hmmm, my pinion seal and bearing are shot and it's going into the shop tomorrow, so if the ring and pinion are bad I'll switch to the 3.07. If it's just a seal and bearings then I'll keep the 3.54. It's a GMC chassis anyway, so the standard 3.07 or option 3.54 is correct.
I'm debating on whether to swap the cab and motor to make it 100% GMC or swap the frame to make it 100% Chevy.
