Sounds like they might have given you a 3100 shock. The rear shocks for the 3200 and 3600 are longer than the 3100 for '55/'56 ('57-'59 the 3100 uses the same shock as the 32/3600).
The Monroe number for the rear is 37188, 83634 in a Sears number (same shock, different part number).
bill, your the man. i am always amazed at your knowlege.
keep helping us guys out, we love it.
leonard
