Ray, I made a jig for the '64 rearend, then carefully washed the mounting brackets and trailing arm bracket off the '64 rearend. I cut the brackets off the '75 rearend, then put the '64 brackets and the '75 rearend in the jig, tacked them in place, then had them TIG welded.
Check the website; I documented the swap.
http://bkndsdl1.home.mchsi.com/rear_end_rebuild.htm
