Today I finally got going on a project that's been in the planning stages for the past three years: Replacing the Schwinn crank on my '73 Super Sport with a Nervar Star. This bike was built as a copy of my first ten speed (remove as much weight as possible, tubular rims on the Schwinn approved hubs, Huret downtube shifters in place of the Schwinn stem shifters), and I've got a lot of fond memories. But that crank eventually had to go. I'd always hated the kludgy conversion bottom brackets available in the past, and when I ran across the alloy Ashtabula to English bottom bracket adapters, I figured I'd give one a try.
The adapter fits up very well. One caveat: It's designed to be used with modern sealed bearing bottom brackets using the internal splines tool to assemble. I'd originally hoped to use the original Nervar bottom bracket, but the cups are recessed into the adapter so the chainwheel side cannot be tightened down. There's no way a 36mm wrench can grip the flats. I ended up using a 68 x 110 Shimano with gave me identical chainwheel positioning to the original Schwinn.
Still looking for an answer regarding the rear derailleur. The current rear . . . . . well, it shifts like a Huret Allvit. Restrictions are that it must be French, 70's, and either take the Schwinn long arm or have one of equal length. Prefer to keep the drivetrain all Huret if possible. I'd already tried converting a Huret Svelto to the Schwinn arm (mounting points are identical) and, if anything, it shifted worse! And no, I do NOT want to put a Sun Tour on the bike, no matter how proper a 70's solution it is.