Did you mention whether the bike had a steel frame or an aluminum frame?
I'm a bit surprised that anybody would have sold a 126mm frame in the 90's. Perhaps early 90's or late 80's? Or, even look to see if the seat stays are bowed in like someone put in the wrong wheel?
Anyway, I mentioned how you could make a 8/9/10 speed wheel work in 126mm. But, you may choose to simply respace the frame so that you can share wheels between bikes. One size fits all. It could simplify your life.