Any Dodge or Plymouth V-8 a-body from '73-'76 should work. The 7 1/4 rear has 2 1/2 inch diameter axle housings where as the the 8 1/4 rear has 3 inch tubes. That means you will also need the shock plates from the donor car and you'll have to use the larger size u-bolts to mount it to your springs. Another obvious difference is the differential cover for the 7 1/4 rear will have 9 bolts. The 8 1/4 rear will have 10 bolts. The 7 1/4 rear is vented through the bolt that holds the brake hose/line tee, and the 8 1/4 has an external vent tube and hood on the passenger side of the housing at the top. There are probably many more differences to point out, but these will be obvious at a glance. Hope this helps, and good luck with your project.8)8)
