I have had a C6 GV in my 89 for 14 years, I love the combination. Just recently I had tranny "built" Full manual valve body, 6 pinion planataries , Clutches, BD torque Converter etc. all the good stuff. it works good behind the Cummins, and with the BD TQ, the trans will hold me back when down shifting.
That said, If I had the option I would have gone with the E40d. Reasons why not, Cost, Aftermarket stand alone computer, Cost, shorten the rear and lengthen the front driveshaft, and cost. I would have wanted a BTS tranny so $5k just for that.
My C6 cost me 1300 and it is a bullet proof setup.
The E4od with lock up will run lower RPMS on the highway than a C6 with GV. and I believe so will the ZF5.
Either way you go I see no reason not to run the GV since it bolts on the back of the transfer case. You will love it running empty, and you could also use it for a splitter.