Okay, got it. There are several variants of the NP-231 and the NP-241 with creative names like Select Trac and Command Trac.

Anyway, your issues is with vibrations when you hit 80 kph (about 45-50 mph is I have the conversion right).

Tom Woods does produce a quality drive shaft. I am sure he can make one that is within tolerances.

As you have mild driveline angles, there are other factors that have could be contributing to you vibrations. I recall some past threads about vibration in the forums. Search for "driveline vibrations".

I have had vibration issues that were resolved by replacing the transfer case mount. I like to look for the simple (cheap) solutions before swapping high cost parts....