I've got the ultimate Frankencrank available. The crank arms are Origin-8 Propulsion. Bolted to it are a 52T ring from an old Shimano 600 crank (slightly worn teeth) and a 38T Salsa ring (no pins or ramps) which is nearly new. It's all 130 BCD. If my calculations are correct, this needs a 113mm bottom bracket.
I've also got a Shimano UN53 square taper bottom bracket. I believe it's 115mm. I picked this up at the Joe's Sports going out of business sale and have never used it.
Interested in trading for cantilever brakes if you have a model I haven't tried. Open to other possibilities.