Originally Posted by NumberDummy
The hub itself (D8TZ-1104-E) fits one 1988 F250 with a parts list of # 30.5AA (4500 lb. capacity with a 4.09 ratio only), and all the 1979 F250/F350's with parts lists of 30.5AA / 30.5R / 30.5S / 30.5Z / which are the only parts lists shown for F350 4WD's.
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You may be reading too far into this. The 80's model trucks with Dana 50s and 60's used a Warn design locking hub that did not use an external spring. 78-79 Dana 60's used a Spicer locking hub which used the spring. The wheel hubs don't make a difference as the aftermarket locking hubs will fit either way.
FYI, the Dana 61 is merely a rear application Dana 60 with a specific housing and carrier to run tall, fuel economy gearing (3.08's). There are no D61's used in a Ford front end.
Jason