? on 7 1/4 to 8 3/4 rear end

Had that done on my 1972 dart back in the day , shaft had to be cut down . I brought mine to a shop , they cut it down balanced it and made sure it fit properly . never had a problem after that .
Nice car you have , going to go well with 360 , 8 3/4 is needed for sure . I must have blown 4 7 1/4 diffs before I got smart and put in an 8 3/4 .