chances are his trans doesn't have a 2.94 first gear. Those were used in the 80's when 2.45 gears were common. Not all 904 trans have 294's many were the 2.45..which I like better cause 2nd is 1.45...with the 2.94, 2nd is 1.54, the engine bogs down on the 1--2 shift, not squeal the tires like the 2.45 to 1.45 shift.
Carriers all fit but from 97 on up the axles are 29 splines, the older axles are all 27 splines, so you need a 96 or older carrier.