It's not my favourite Klein colour, but as usual it's an amazing looking bike. Last summer I passed an older woman on the rail trail who was riding a smaller Klein moonrise. I still kick myself for not giving her my number and begging her to sell me the bike when she's no longer riding
I support the opinions on your update ideas: don't do it like that. If you gotta make changes, consider...
1. Mathauser or Kool Stop pads, clean rims and good adjustments are all you need. Your brakes look like Dia-Compe 987's. They're good canti's. If you really need to improve the brakes, try some old XTR M900, or Avid Tri-Align canti's with good pads.
2. If you like the grip-shift, Ritchey's old canti levers were good and had a nice finish. I think they were made be Dia-Compe. I just prefer Shimano's rapid-fire's myself.
3. That fender isn't long enough to protect your downtube from rocks. (You know it won't do a thing for you in Portland rain either.) The best way to do that is you exercising caution when you see stuff on the trail ahead.
4. Tubeless? C'mon, you've got good wheels there. Use 'em. Mount some good tires and have fun.
5. Ya, the pedals do look out of place. Ebay, or a good LBS could turn up some good 747's.
You know you've got a wicked handling, mint condition piece of history that is no longer made. Treat it with that kind of reverance. Lewis River, Plains of Abraham, Mackenzie River? Sure. North Shore, Whistler, urban or bike park? Nooooo!
Oh ya, Enduro Fork Seals still makes replacements for the Mag-21.
Many excellent points