I am having trouble following what you are asking.
-you have a '53 3600. Is the 52 axle above the springs?
-you have a '66 1/2 ton rear end which you would like to use.
I don't understand what the PO did or why. That doesn't really matter. What does matter is that you put the '66 axle on the same side of the springs (above or below) as what was original.
You will need welded-on spring perches which are the same width as the springs and 3 inch radius u-bolts, and a plate with holes in the right places.
Carl


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission