Bicycle Mechanics - Component advice for rebuild

I've been commuting since August and have since put in @ 1500 miles on my 1991 Diamond Back Ascent EX. Probably more miles than it had ever been ridden in its entire life. I've looked at and ridden about a dozen new bikes with the thought of more modern ride. Parts are a ***** to find for this thing. My verdict? I like the Diamond Back's ride. Why not do it up with new components? Reduce, reuse, recycle, etc. So, I want to build myself a bomb-proof commuter bike. I want to emphasize dependability and long-term easy availability of replacement parts. Here's the current configuration and pics. Any suggestions on new components? Right now I'm running it as a 1x7 and I'm thinking I want to keep it that way (Portland winters are hell on the drive train and the simpler the better). I'd like to start with a new drivetrain, probably a single-speed downhill or cyclo-cross crankset with a 39-40 chainring up front. I like running a seven speed cassette in the rear because you can run a wider chain, but maybe I'll have to go 8-speed for parts availability? I'd prefer a 11-? with maybe a 34 bailout cog.

Current setup:
Frame: Diamond Back Ascent EX Tru-Temper Chromoly; Wheelset: Araya RX-7 rims w/ Forté Fast City ST/K 1.25x26 tires; Derailure: Shimano Deore LX FD/RD-M550 (only using rear); Front Crank: Shimano FC-M550 175mm w/ Shimano SG C-36 chainwheel (originally 46-36-24); Rear Casette Shimano G30-26-23-20-17-15-13; Brakes: Shimano RB/BR-M650 Center Pull callipers; Shifter/Brake Levers: shimano STI-M060.

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That's a great commuter bike. What parts are you having trouble finding for it? Perhaps you're looking in the wrong place 'cause there are plenty of parts available for that bike.

Front and rear hubs need new cups. Shimano Deore LX FB-M550 and HB-M550. Both pitted and couldn't find them. Bracket cups showing excess wear and are going to need replacement. I don't mind the cranks themselves, but would like to get a new chainring (39/40 tooth). There are a several broken teeth on chainring (I have vague memory of a pretty bad spill in the early 90's, probably the same one that broke the left shifter). Couldn't find a replacement STI shifter/lever so I just hacksawed the shifter off to run it 1x7 while I purchased another trigger shifter, then ealized I didn't need the other rings. Steel chainring for longevity? Have lost the chain a couple times on downhills since converting to 1x7. Chainguide? I hate adjusting the cantilevers. Despite following the exact shimano instructions (found a mountain bike maintenance book from 1992 w/ original instructions) for installation, it still seems like magic when they actually get dialed in. And even more so if they stay that way for a hundred miles.

I suggest just buying new wheels rather than trying to fix the hubs. MTB wheels with a 7sp freehub are easy to find.

For the shifters- if you're sticking with 7sp (which is a good idea in my book) I'd ebay some XT or Deore thumb shifters and you're good to go for a long, long time.

To keep your chain on, you could just get a cheap FD. For what it's worth, you might as well run the triple since you're likely to find the shifters as a set anyhow.

Cantis do take practice to adjust properly, but get them set up right and you won't look at anything else.

I'm currently using a '92 Miele mtb as my commuter and it actually gets more mileage than any of my other bikes just 'cause it's so damn great.

http://bluecollarmtb.com/blue-collar-bombproof-bike-project/

For the shifters- if you're sticking with 7sp (which is a good idea in my book) I'd ebay some XT or Deore thumb shifters and you're good to go for a long, long time.

Yup, and if you find the opportunity to pick up a second set, grab 'em just to keep for spares. I've got a new-in-the-box set of Ultegra 9-speed STI's in my shop just because Shimano tends to discontinue better quality after market parts that don't match the current standard.

I've thought about grabbing more XT thumbies, but not as spares- as extras for other bikes. Perhaps I'm jinxing myself but I don't know if I'll ever actually BREAK a set.

200lb rider + 28lb bike + 10mph + fixed object (boulder in my case) = broken shifter

A simple 3 foot fall to concrete will often achieve the same result.