Getting ready to swap a 5.7 into my 73 Dart Swinger

Ok in a horse trade for some side work I may be able to get a 8.8 rear end from a mustang with disc breaks and im hearing that its already equal short length axles? Please help what length am i looking for? I'll look all night i know ive seen it here before on this site. And I got turned around from the fram shop cause my steering wasnt in at all so I'll be trying this again this next week.. Thats the rear end I'm being offered..20190725_214837.jpg