You may find balancing is not required.

I pulled a balanced driveshaft out of my roadster due to a 9" diff swap and the pinion was 1" shorter on the 3.70 that went in than was the pinion on the 2.75 that came out.

The local speed shop built a new driveshaft for me and when I mentioned I was taking it to the balance shop, they told me to give it a try as was since they'd built more than a few driveshafts for 150 mph doorslammers that were not balanced and no problems reported with them.

The new shaft turned out to be very true and smooth running.
Never did balance it.