The difficult thing about most of these recent conversions is that the bikes are all older 6 or 7-speed drivetrains and the only new parts that are available are for 10-speed. I'd love to find a nice cold-forged, square taper triple with 110/74 bolt circle with 52/38/30 chainrings. For now, I've got to find a Shimano Sora triple for a customer's bike, but it seems they are out of stock (and not scheduled to be available until January - ouch!).
Here's a really nice fillet-brazed Otis Guy that I converted to Shimano Ultegra SL triple cranks. This bike came in with a nice Campy 53/39 (that went onto his other bike replaceing a 52/42), Sachs 7-speed freewheel, and Dura-Ace 8 speed down tube shifters. On went a new Ultegra SL triple, Ultegra derailleurs for triple. Stayed on the bike were the Dura Ace 8-speed down tube shifters and Sachs 7-speed freewheel. Connecting the cranks to the freewheel is a new SRAM 8-speed chain.
I had some issues getting the 8-speed shifters to move the derailleur. It worked well between the first 5 cogs, but between the final 2, it required too much fiddling for me (but was something the owner worked around for the past many years). It had the original Dura Ace braided cable and spiral wound brake type casing. I swapped this out for a new SIS cable and compressionless casing and, bam!, worked like a champ. I have an old Sachs 8-speed freewheel and measured the cog spacing and found it was the same as the 7-speed spacing, so figured, the indexing of the 8-speed shifter should be compatible no the 7-speed freewheel. Bingo!
The bike turned out really nice. I really like taking older bikes like this and updating them with new parts. It's like giving the bike a new breath of life - and a nice bike like this deserves to keep on rolling.