Some answers, and more questions.
All 1954 Mercs except station wagon used a Ford rear axle with removable center similar to the 9 inch, but with a weak 8.25" ring.

1954 Merc station wagons used Dana/Spicer 44 with a 8.5" ring.

ALL 1955 and 1956 Mercs used the Dana/Spicer 45 with a strong? 8.75" ring, which is not a Dana 44, but similar.

1954 Mercs used 4,5" bolt circle, same as Ford.

1955 and 1956 Mercs used 5" bolt circle.

Questions:
Is a 1954 Merc passenger rear end identical to 1954-1956 Ford?

Has the 1964-1966 Mustang 9" rear end the same spring pad distance as the 1954 Merc?


Which rear end yokes are the same on 50's and 60's Ford/Merc?

1955 Mercury

merc. used the same dana rear as ford f-100, up to 56, with pick-up bolt pattern, dana. when I tore up the rear end in my old man's 51 f-100 pick-up, we used a early 50's merc. rear because the local yard didn't have a pick-up rear.

 lincoln/merc. y-blocks &mel's                                                               bucyrus, ohio.