My Ebay "93-98 Grand Cherokee Steering Shaft" came in this week. I used a die grinder to open it up at the firewall end, made a notch in the in the steering column shaft with the Dremel, and she bolted up like a charm. Total install, including fab, was probably two hours. The bolt threads in both ends of this particular shaft were 3/8-16 (I thought for sure they would be metric).
Comparing the Jeep shaft to the stock Monte shaft.
Modified and being installed. That's Anti-Seize in the opening; used it for lube as it was in arms reach.