Originally Posted by 52Carl
-you have a '53 3600. Is the 52 axle above the springs? 52 3600, axle above springs
-you have a '66 1/2 ton rear end which you would like to use. correct
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. below the springs as 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

Gotcha. Found some 2" wide perches that should mount up to the 66 rear. Thanks for the help!