HELP! Shortening my driveshaft

After you put the car together, you will measure the distance between the trans out put shaft and center of joint as it sits in the end yoke.

Then you tell that info along with the trans and series joint the diff uses and see a driveshaft shop, machine shops don't balance driveshafts.

You have a few driveline shops in CA, if you can't find one, see a big truck shop and ask them who they use to balance there shafts.

Might be too late now, but i would send that tci trans right back and see Martin Saine perf, especially since you are in CA