In the end I gave up on that idea lol. I think one more trip to the hardware store would've got it working but I was at the end of my rope so snagged a Sachs-Huret Hi-Stepper from another bike that's awaiting an overhaul.
Went on the first ride and sure do love these retrofrictions! First time using them.
One issue though - front derailleur won't shift to the smallest ring when I'm riding. It works on a stand. I'm pedaling very gently and it's not the limit screw. I've searched the problem and could be a variety of things.
Since I switched to a triple, with a longer bb spindle, maybe the small chainring is too close? I could add a spacer on the end of the axle. The hi-stepper curve doesn't really match the chainring. It won't go any lower, I could try raising it or angling it differently.
Any suggestions on where to start?