paul, because im to stupid to figure out who to get your pics into this reply your going to have to deal with my feeble attempt to describe the parts.
52-e54
used the short offset (or reduced trail or non parallel of you prefer) steel top tree. has 4 mount bosses.
L54-56 & 57-58 sportster uses the long offset version of the 4 boss steel tree.
59-E62 used the 2 boss steel tree.
L62- 72 uses the alum tree with the press in rubbers
73-87 uses the alum with the non press rubbers.
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the 1st alum rear mount used on production bike was for 1961 models.
that mount had a desigm change mid 62