Originally Posted by
bradtx
If I had to make a swap I'd use FB's method, but I think if it's only a matter of tires I'd opt for another set of tires.
Brad
PS If your drop outs measure 132.5 mm, no shims are needed.
To add to that, spacers also may not be needed with 135mm spacing on a steel frame. Whether to use spacers or spring the frame closed, depends on the stiffness the rear triangle, your strength and your patience with trying push a wheel into place while using two hands to spring the frame.
I only suggested the spacers because I inferred from the OP that he wasn't comfortable with springing the frame closed.
When I think about stuff like this, I divide it into three groups; in a pinch, occasionally, and steady diet, and decide how to proceed accordingly.