Ok if we're talking rear diffs then here goes. What can I get an axle assembly out of that will fit under my Aspen other than one out of a v8 Aspen if I can't locate one locally. Now what my car is doing is that it's making a chunk chunk noise when I get on and off the gas. The drive shaft is new so it's not the u-joints. Could that still be the spider gears? In my 7.25 rear diff. Thanks for the help.

In mopar alphabet soup is F/M/J bodies.

You can enter your car into www.car-part.com and it will do the interchange for you.

If dealing with mom and pop in BFE thumbing through the old red or green copy of the Hollander guide you want:

F-Body: 1976-1980 Dodge Aspen/Plymouth Volare and all variants...
M-body: 1977-1988 Diplomat/Le Baron (RWD)/Caravelle(RWD), Fifth Avenue(RWD) and 1982-1988 Plymouth Gran Fury (lots of old cop cars made in these bodies with 2.94 sure grips...)
J-body: 1980-1983 Cordoba and Mirada

-D.Idiot