There's 3 different diffs used from '60-'72 on Chevies, the 9 3/8" w/drop out 3rd memeber ('55-'62 style), and 2 variations of the 8 7/8" 12 bolt truck diff. There's not much available for the first one as far as gears, the 3.38 and I think maybe the std 3.90. There's not even a good limited slip for them. As far as the 12 bolt goes, gears are easily available, try Randy's or Precision gear, I think most ratios up into the low 5s are available, though some do requeire a different carrier. Also, if you're looking for a lsd for a 12 bolt, there is a mid year change in '65 from the early 17 spline to the later 30 spline, no lsd being made for the 17 spline. Axle shafts can be swapped, though, to change the spline. Also, with a little machining to shorten and re-groove them, the '71-'72 axles can be used in the '63-'70 housing to convert to 5 lug.
