Finally back on the road after a successful auto to M46 swap!! Thanks so much to everyone who posted answers and suggestions. You helped make this newbie's first project successful and fun (mostly). It shifts really smooth, and runs nice and peppy.
I used STS Machining's slightly lightened flywheel, and the Sachs clutch kit from IPD. I was able to get the original clutch cable off the 1985 donor car. Along the way it got brand new bronze shifter bushings, shifter cage bushings, engine mounts, trans mount, center bearing, rear main seal, and breather box/hoses/flame trap. I haven't swapped the differential/rear axle, but have it sitting in the garage in case I decide to. Once I got the O/D working, I haven't found the RPM's at highway speed to be particularly high or at all annoying. After some minor troubleshooting, overdrive works flawlessly. I used a new O/D harness from Dave Barton.
The upward-pointing arrow light in the instrument panel goes off when overdrive is engaged, and stays on at all other times. Is that backwards? If so I'll probably just leave it that way rather than try and figure it out.
My only major glitch is a serious oil leak that was not there before this project, but I will put that in another thread.
Thanks again everyone!