Well the first part is easy, Dana 30 front, AMC 20 rear, should be wide track. Ratios vary, 2.73,3.31,4.10? There is/was a tag on the dana with the ratio but they are rarely there and readable on a Jeep that old. Numbers stamped on the AMC 20 can be deciphered to tell the ratio but you will have to find the codes. My 86 Laredo came with 3.31 gears. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Oh, here's the codes.

Wide Track AMC 20
Code Gear Ratio Diff Type
D 2.73 Open
DD 2.73 Trac-Lok
B 3.31 Open
BB 3.31 Trac-Lok
A 3.54 Open
AA 3.54 Trac-Lok
H 3.73 Open
HH 3.73 Trac-Lok
C 4.10 Open
CC 4.10 Trac-Lok

The code is stamped on the housing boss to the left of the diff cover right near the axle tube.