I have taken on the hopelessly romantic task of rehabbing a 1974 Motobecane Grand Jubilee and need some advice on frame alignment.

I built a nice (and cheap) copy of the Park Tool frame gauge. Follow this YouTube link for your DYI'ers out there:

https://www.youtube.com/watch?v=z9bPiAi_KQc)

Sure enough I found that the rear stays are not symmetrical. I also measured using the old tried and true string test. Both methods yielded the same result… the drive side dropout sticks out about 3/8" further out than the non drive side. Spacing at the rear dropout is currently at 121mm.

I have no problems getting out the ol' 2x4 and leveraging things back, but which stay to bend? Is the drive side too far out (therefore making the non drive too close to keep the 120 dropout distance) OR is the non drive side too close, so I need to bend it out, but then shove the drive side in a bit to keep the 120mm spacing correct?

Seems to me one has to establish a centerline off the head tube/seat tube line then symmetrically space each drop out from that reference line, all the while maintaining your 120mm drop out distance. I'm I missing something here? It really has me bent out of shape!