Shortening your driveshaft.
Step 1 would be determining how long it needs to be. Measure carefully write it down. carefully measure the one you cant to shorten. measure it extended and retracted. Next decide if during its intended range of motion it extends more than it retracts or the other way and come up with a measurement of how much you want to remove.
After looking my driveshaft over I decided to trim off of the fixed yoke end.
I ground the weld flush and I could just make out the parting line
Using a zipcut I grind in about 1/8″ until I can see a parting line. You don’t need to go deep.
Then when you get it cut all around tap it with the hammer
If it moves tap it out the rest of the way.
Make a mark on the tube how far you want to cut it. In my case 4″
I used a piece of emery cloth as a wraparound to get a straight cut line.
Start cutting (zipcut) Go slow, take your time. It matters.
Here is one of those great tricks! add around a cup of ATF to the inside of the tube before you put it together. It prevents rust and helps to balance the shaft and/or dampen the vibrations.
Carefully line up the 2 yokes when you assemble it. It matters
Tap it together with the hammer, again take your time.
It should be a fairly close fit when you are done.
Stitch weld it and don’t miss a spot.