Wanted: Your old, smelly spd shoes 9-10.5 UK, 43-45 Euro

One concern with the boots, though, is that they didn't have the stiff soles of cycling shoes, and plain tee nuts might pull through the sole in hard use. I made reinforcing insoles out of high-strength sheet steel roofing metal, and put the nuts through the steel insoles, spreading the load over a much wider area. If you don't feel up to that, just buy some stainless safety insoles from an industrial supplier like McMaster Carr Industrial Supply.

Wrong - use salvaged cycling shoe insoles or gtfo.