Minor progress
The replacement pivot tube bushing arrived and was installed.
I discussed my handlebar twisting with my LBS mechanic which lead me to discover the pivot clamp on the steerer extension tube wasn't tightened down. After tightening that clamp the handlebar no longer has twisting problems (for now at least).
There was a kind of flat spot on the rear wheel which was very noticeable (as a significant vibration) when I got up to speed. I brought it to the LBS and the mechanic checked it out on a trueing stand. He suggested I dismount the tire from the rim then remount it. After that it seemed a lot better, I guess the bead wasn't on the rim quite right.
I brought out my dremel (well, B&D's clone), bought some cut off wheels and with some difficulty cut off the disc brake mounts from the suspension fork I've got. I partially disassembled the front triangle and went to test fit the brackets to the new fork and discovered I had a lot more cutting and grinding to do. So I reassembled the front triangle on the bike with the rigid fork. I checked out possibly using a different hole on the FWD bracket to bolt on the fork but there was a small eyelet on the fork which prevented the FWD bracket from rotating to a reasonable angle. I wanted to do this to increase the trail a bit, with the rigid fork the front end is a few inches closer to the ground, increasing the head tube angle which decreased the trail. I may try to dremel those eyelets off a bit, I have no idea what they are for.
I looked at the old front derailleur again, the 34.9 marking on the inside bothered me a bit. I wondered if you were supposed to cut off the plastic liner if you wanted to mount it to a 34.9mm tube. Eventually realized the liner was actually removable with a good tug and now the derailleur will clamp to the TFT sleeve--I don't need to acquire a new derailleur after all. I've mounted it to about the right spot, broke the chain and threaded it through the derailleur. Reconnected the chain and adjusted the low limit screw. Now I need to cable up the front derailleur and finish adjusting it.
I'll eventually need to buy a new chain--the old chain is too short. The original distance from the original bottom bracket to the rear axle was 17". The new front bottom bracket to the front axle is 18". I can't get into the two lowest gears with the the chain on the largest chainring. Once I get the front derailleur cabled up, this limitation will be moderately tolerable, but still...
Further future, I am interested in getting a larger big chainring. I've currently got a 42/34/24 in the crankset. I suspect I'll need to change out the whole crankset and the front derailleur at the same time--the current old derailleur apparently won't go any larger.
Todo list:
1. cable up front derailleur and adjust
2. shorten brake cables
3. redo cable to frame mountings (ought to have a discussion about this: ziptie, tape, velcro, etc)
* replace chain with longer
* acquire and try a cruiser-style handlebar
* reapply loctite to bolts that need them (I've screwed and unscrewed pretty much everything at least once)
* install TFT safety bolt
* install insert collar
* more cutting and grinding of suspension fork
* improve drive train (go to 8-9 speeds on cassette, bigger chainrings on crankset)