Should be easy but... You mentioned that you've already measured the hubs and the diameters and spoke hole distances are the same but that old nemesis optical illusion makes the red plastic dust covers look smaller.
Assuming that the hub with the cogs on it is the Maillard 700, it's going to be mechanically superior to the other hub that has the plastic dust covers.
Obvious suggestions:
1. Pull the freewheel. Check to see if it has Metric or British threads. Maillard hubs came both ways.
2. Take apart the Maillard hub and check the cups and cones. While you have it apart, clean everything up, replace the 1/4" balls with grade 25 chrome steel ball bearings and repack it with quality water resistant grease.
3. Are the rims the same? If so, you're home free. Use the stainless spokes from the Maillard wheel.
I checked all of my data on hub dimensions, Sutherlands, Spocalc etc. and none of them had the specs for the Helicomatic (Normandy Luxe Competiton) or the Maillard 700 hubs. My 3 versions of Spocalc spoke length calculator have just been deemed useless.
They have dimensions for all kinds of weird hubs made by folks with a machine shop that made maybe 20 sets during the late 80's and early 90's but nothing about some of the more common hubs used on French bikes and Trek - Maillard 700s and Helicomatics!
Measure the spoke lengths from both wheels. On clincher rims like yours, spoke lengths can be 2-3mm too short or too long, it doesn't matter if they are close.
Some OCD's will jump in and dispute this claim but... Reality is reality and that's what happened with many factory built wheels. Rear wheels were made with the same length spokes on both sides of the hub regardless of the wheel dish!!! DOH!
Several other suggestions:
1. You can cut out old zinc plated spokes in the Helicomatic hub (after you've pulled one to measure it).
2. Loosen the spokes in the Maillard wheel.
3. Line up the spoke holes in both rims and tape them together then you can switch spokes from one rim to the other being careful to cross them the same.
4. Redish the rebuilt wheel.
Done this many times...
verktyg
