8-1/4 pinion depth shims

The 1975 TSB states the position and part number of the shim changes sometime in 1975.
It says either type could be found that year.
By 1976 they all were changed to the newer style.
The earlier shims part numbers were 2931960 - 2931978. Thickness of each shim can be found in 1974 Chrysler parts catalog.
Sometime in 1975 the newer shim was introduced part numbers 3723620 - 3723637.
Don't believe the earlier shims are made any longer but most can still be found on eBay.