8 3/4 from 66 to 73

[66charger73]

If I took an 8 3/4 from a 66 charger and put it in a 73 I would most likely have to relocate the spring perches and just get wheels with about 1 1/2"'s less backspacing correct?

[John_Kunkel]

The '66 spring centers are  3.3" narrower than the '73 (44" vs. 47.3"). If the perches on the '66 were moved out 1.65" on each side there wouldn't be enough room between the perch and the housing stepup for the U-bolt.