74 duster 8.25 swap into 65 Dart 7.25?

[Stumpy]

So here’s the deal. I was hoping to get an abody 8.75 made out of unobtainium but someone has offered me a free 8.25 diff out of a 74 318 Duster to replace the whiny 7.25 in my 65 273 HiPo 4 Speed car. I think this Diff would be more than adequate. The info he has says the spring perches are the same and should bolt up but the overall width is 1.8” less. The 8.25 appears to have 2:94s so it’s the carrier I want. It will require the driveline to be shortened and balanced. I don’t know the condition of the gears. It has LBP drums on it (which is fine for me) that I’ll rebuild.

Has anyone done this swap? Any problems I need to watch out for? If I get it I’ll need to get LBP wheels to replace the 14” rallyes on the back. Is there a particular size wheel that would fit well considering the width of the diff? Would 15”X7”x4.5 work? What tire will fit without modification?

 

[junkyardhero]

you'll need the 8.25 shock plates and new U bolts to fit the tubes-- they're bigger than the 7.25

the driveshaft will need to be shortened.

i ran 15X7 w/ 4.25 back space factory cop wheels on the back of 64 & 65 darts with 8.25's with no problems.

 

[RustyRatRod]

Cept the drive shaft, it's a bolt in swap with all the right pieces just like hooha up there ^^^^ said.

 

[memike]

Bolt right in, and yes little over an inch narrower, I did all this to my 66 Valiant and have 7 inch police wheels on it now, you actually will have 5" back space

 

[gtxdude]

I did the same swap several years ago into my 65 Dart, 8.25 LBP out of a 74 Duster. And what they said above with the wheel and tire size.

 

[cudamark]

If you're going to spend money on that driveshaft to have it shortened and balanced, you might consider replacing the ball and trunnion joint with a slip yoke. Down the road, that will be an easier one to get parts for and simpler to repair.