if you have 10 hole rear wheels you can use the late model rear from an r.v. or 3500 series gm truck. wheel size on that rear end is 19.5 which is only a tad bigger than a 16 inch wheel, however the 20 inch stock wheels you have will bolt to them. there is a slight difference in wheels, but i have seen the late model diff with old wheels and it seems to work. you can also just install the late model diff and change the entire set of wheels to 19.5. on the late model diff is much wider brakes and better friction material for increased stopping ability, but remember the front brakes are very important to, so there's the weakest link. 70 mph with the bolt ought to be pretty easy to attain, with an improvement in stopping ability. maybe milage of about 10 or so. if you change the diff, i would sure switch to a dual master cylinder, as there is definitly a weak link in the ability to stop.
ought to be a pretty easy swap, and sure makes sense to me.
