I can chirp the tires easily with a good 283 and the stock 3.90 rear is 53 years old, and although it's used mostly for town driving and load hauling, I cruise it at 65-70 when on the highway no problems except a bit too much exhaust and road noise .... the 3.55 gears would be as much improvement as needed for more highway time, although I'd be inclined to go with an OD trans and leave the rear - my next truck will have a 700R4 with the 3.90 rear, trucks should be able to haul a load
Bill
