The 120 rear spacing can be widened using the cold set method (wedge a 2x4 in the frame and push) the safe suggestion is that you can go one size more so 126.
This will broaden your options for wheels.
It's a track frame that has the current track hub spacing, why in fucks name would you want to widen the spacing???
It's a track frame that has the current track hub spacing, why in fucks name would you want to widen the spacing???