What and who are the current favorites for machine work on heads, cases, cranks, etc.? In other words, for a comprehensive rebuild, what would you do for heads and valves, engine case, and crank shaft? And who are the established sources?

Bonus points for shops near Denver or Tucson (and Phoenix).

If it matters, I have a 1973 2 liter, and plan to run the stock FI.

I think Competition Engineering in Phoenix is one of the best air cooled 4-cylinder rebuilders (including 912/356) in the Southwest. CE did my 1911cc machine work and I put 30K on it mostly spirited driving with zero issues. Dan has been building street and track motors for30+ Years.
I now work there part time so feel free to PM me if you want to talk.

Thanks, Michael.

Any other suggestions?

I'll second Competition Engineering. I've known Dan for 30yrs and the machinist he uses for 40. All nice people.

Does Fat Perf / Rimco do good work?

AJRS
In grand junction is a 914 racing shop that specializes
In 914’s

They do a lot of the matching for the Denver porsche shops

For heads I go with Len at HAM as he will use the new castings and rebuild those to better than stock with high quality valves, seats etc. Plus get the coating work done too to keep the heat out of the heads and in the exhaust.