I recently changed the 3.42's in my 1992 GMC shortbed to 3.08's and I am extremely pleased, my gas mileage went up 1 1/2 to 2 Miles per gallon and driveability is improved. I have the 350 engine with over 310,000 miles on it, kind of tired but works quite well. I would recommend the 3.08's as a great driving gear especially if you do much freeway driving.
