How to identify how much to shorten driveshaft?

I'm doing a D60/D70 swap from a 92 W250 Cummins truck into a 74 Ramcharger.

The rear I'm having a new driveshaft made so due to the 1410 Yoke requiring a 3.5" tube.

On the front. I'm able to wrestle the front shaft on by fully compressing the slip joint, but this leaves NO room for the suspension to travel and further compress the slip joint which will obviously be an issue.


I know that the D60 has a longer pinion length than the D44, bu how much I don't know, but how do I know how much to have the shop cut down my driveshaft? Do I just take a SWAG and call it 1.5"?


(SWAG = Scientific wild a$$ guess)

just taking a SWAG id say see how much clearance there was with the D44 then have it shortened that much for the D60,if there is a pattern of where the slip yoke was riding with the 44 you might be able to use that as a SWAG measure!

I talked to the guy who owns Brutal OffRoad in Bandera (a big mopar guy that not only knows everything mopar, but especially the trucks)...

he gave me the detailed instructions on how to measure for proper distance and and said it'd be somewhere between 2-3".

I looked at the wear pattern on the slip joint, and I can see where the the seal originally rode, then it changed as the stock springs wore out; and by taking 2.5" off the shaft, it'll put the slip joint right back to where it was originally.

I put my car on the trailer and took it to the driveshaft shop and let them do the measurement....

How about measuring from the center of the axle tubes to the U joint mounting surfaces on all the rear ends and subtract the differences to have your drive shaft made and or shorten

that would've been the easiest way to make up for the exact difference in pinion length between the D44 and D60. I've already dropped the shaft off and told em to whack 2.5" off of the front based upon the wear patten that was visible on the slip joint from the seal, I could see where it was when the truck was new, then as the springs aged and sagged it compressed. Now with new springs and new front axle, 2.5" puts it back where it was in the beginning.