Newbie Dart Axle question

My first post of probably many. Been reading this excellant site and have a question.

Finally after many years I got another Mopar. Actually 2. Picked up a '73 Swinger parts car with a 318 2bbl and a '71 Swinger with a 225 slant 6. Both have 7.5 axles under them. The '73 is large bolt pattern of course.

Question is, to get the large bolt pattern that the '73 has on to the '71 can you just swap the axles and brakes or do you have to swap the whole rear end between the two cars? If just the axles and brakes can be done how hard is it to do? What is involved/anyone done one?

Only ask about going this way as I know the 7.5 in the '71 is good as the car runs and drives fine. The '73 internals are unknown as the car is not currently running and driving.

Will be doing the small bolt pattern front disc brake to the large bolt disc brake swap off the '73 and want to match the bolt pattern for the rear.

Would actually perfer an 8.25 for the back, but as yet found none locally (ABQ, NM). Will need one when I get ready to do the V8 swap in the '71.

Any help is appreciated.