The Stanley 45 plane used blades that were 1/8” thick. The width can be anything that will fit within the lateral movement of the side skate.
The blade is retained by a wedged bolt on a wing-nut arrangement, but it is notched at the top right hand side to take the adjustment peg.
In theory, you can substitute any blade of the same 1/8” thickness, (all the Record 405 blades, as well as most of their parts are interchangeable with the 45).
If the notch is not present on the new blade, either file one in place or move the adjustment peg out of the way and rely on using the retaining bolt only. The Stanley 46 plane, a close relative design-wise, used only the retaining bolt. Getting the adjustment right is not difficult.
In short it’s the thickness that is really important.
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