7 1/4" to 8 3/4" rear end swap advice

1968 Dart 270 said
Hi,My car came from the factory with 10" brakes. The rear has the line and vent down on the drivers side axle tube (70 style). It came with u bolts and the shock plates. Will I need the c body rubber line for this style? The rear did not come with leaf springs but mine are still in my car,along with the 7 1/4" rear. My car is small bolt pattern,this rear end is small bolt pattern so no need for new wheels.
Are you sure On those measurements? Dana67dart posted a factory parts sheet saying the measurement for a 1967 with 273 an a904 and 8 3/4" was 52 1/2" with 3" diameter and I've had several other people contact me saying 52" as well. Just want to be sure so I can hunt for the right driveshaft. Don't want to cut mine down if I don't have too. Buying a factory correct one takes all the guesswork out of it and want to go under the car with everything I need to tackle it in one fell swoop.
There are some.other remembers who have posted that their cars came from.the factory with an 8 3/4" rear (10" brakes) but their car had 9" fronts. My car has 10" brakes,but im.curious as to big of a deal thar is to have 9" on front and 10" on back if Chrysler made some.cars that way?

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I think what I would do is install the rear end and see if the rubber line will reach the splitter block. It being on the drivers side tube will be better than on the hump of the center housing. Same with the brakes, I think what you have will work, and since you have small bolt pattern, there is no concern about a mismatch. Now, for the driveshaft, if it’s a 52” driveshaft, that is a really common size, and once you get the rear end in, you can confirm that is the size you need. I wouldn’t buy one until you do. Maybe it’s a Dart thing, because the Dart has a 111” wheelbase, and Plymouth cars are 108”, and the difference is all in the rear floorpan. I probably have 3-4 52” driveshafts here, which is the common size for a 318/904/7 1/4” drivetrain. Again, you have the parts to install the rear end, I would get it in there before spending any money on parts until you confirm that you need them. It may take a little longer, but it saves from buying parts you may otherwise not need.