Roger,
If you still have the later 4HA such a swap is easily done. The modern
Dana/Spicer Model 44 is virtually identical to the late Salisbury 4HA’s. The
Dana 44 was used in Ford trucks, International Harvester Scouts, Jeep
Cherokee’s and many others. The currently available Dana gearsets generally
have a fine spline pinion shaft, so you would need to purchase a new
fine-spline companion flange to mate to your 120 driveshaft. All sorts of
limited slip or locking differentials are available, but you need to make
sure you use one with the correct spline count for the 120 axles. If you
now have a 3.54 or 3.70 ratio the proposed 3.23 will fit directly on your
existing differential unit, with no axle worries. About the only pitfall I
can think of would occur if you rear axle has been swapped for an earlier
model sometime in the past. The early 2HA’s are a dead issue from a gearset
perspective, having been long obsolete. The early 4HA’s used smaller ring
gear bolts that were not up to the task for sporting use. I have never
taken one of these apart that did not have at least two broken bolts. If
such is the case, you would be best to replace both the differential and the
gears, all of which will fit in you rear axle housing.
Best regards,
Mike Spoelker