125mm hub in 126mm rear spacing
I found a nice, barely-used 27" wheelset to replace the crusty ones on my '85 Nishiki Riviera. The only thing that's different about the new wheels, dimension-wise, is that the rear hub is 125mm as opposed to 126mm. Would that cause any real problems? I would think that by clamping the skewer tight enough, the steel would compress an extra .5mm per side.
Absolutely no problem. Such precision in the frame was never intended in the first place.