Ok, back to this after a month of delay waiting for parts.
I ordered my parts from RockAuto, including what should have been a new Timken input bearing. Note that T-18s use one of two different input bearings, a thin bearing that is 20mm thick (early, what I have) and a thick bearing that is 23mm thick.
The Timken bearing is still listed on their site as 20mm in thickness. What I got was a 23mm thick bearing. Right box, wrong bearing. I contacted them and described the problem, and I exchanged it for another example of the same Timken PN. Same part, wrong thickness. At this point RockAuto gives up, says to send the second example back and we can do nothing more for you.
I've bought T-18 parts from Parts Mike before, with good result, so I called them and bought both the input and output. I asked if these would be quality bearings and their rep said they were sending quality Japanese bearings. What I received was a Japanese bearing for the output and a Chinese bearing for the input. The Japanese bearing seems fine, but the Chinese bearing had a distinct rumble. I called Parts Mike and complained, and they said they'd look into it.
So, they claim that no one but Chinese aftermarket is now making the input bearing for the T-15 and 'early' T-18 (Jeep PN 448 8141). However, their drop shipper (Transtar) offered to go through their stock and pick out one that felt smooth. I said ok - they would ship me another bearing and did not ask for the rough bearing back. Another week passes, and no bearing. I call, and they take a message and say they will call back. I call again two days later, and they say it should arrive July 1. It did, it's indeed a lot better than the first bearing I got.
So the transmission is back together now.
The black steel pipe is my improvised bearing driver that I made from 1 1/4" black steel pipe. Aside from putting the pieces together, I had to grind out the threads on the coupling by about 80 thou, but it works great. The pipe cap on the end gives you something to hammer against, and with a 12" nipple makes the driver long enough to drive the input bearing home. Works on the output side too.
Another complaint about the Chinese bearing - it comes with a snap ring, but the ring is slightly too large to fit under the bearing retainer. I only discovered this after I had driven the bearing on. Fortunately I was able to remove the Chinese ring with the bearing in place and substitute the ring from the original bearing, then the retainer fit fine.
I also got a new cross member to replace the cracked and booger-welded original -
Thanks Ben!