I've already posted this in the bicycle mechanics forum, not sure if that's kopacetic, so apologies if it's not.

Anyway...

I bought a mid-70s Motobecane Grand Jubile frame that the previous owner had cold set the rear dropout from 120mm (I imagine) to 130mm.

I had wheels built around 130mm Grand Bois hubs that will accept either Shimano or Campy cassette. Trying to save funds after that expense, I found an unused Shimano Hyperglide six-speed (14 to 28) cassette in my parts bin.

Bike has the original Huret front and rear derailleurs, and I've read a 28 tooth cog is about the largest the Jubilee can handle. Cranks are 52 and 42 tooth. I don't mind keeping it more or less original gearing, but my question is: since the original chain line would have been for 120 mm hub, what problems am I likely to run into with an extra 10 mm hub width? Would I need spacer of some sort between the cassette and the hub? Or is my best option to run an eight, nine or 10-speed cassette, even though that would be beyond a half-century-old French drivetrain's capacity?

Thanks in advance!