Bill Tindall, E.Tn.
Given what you have said you want to do, and don't want to do, your goal is unclear. Are you using these planes? If so what is the disadvantage of retiring the authentic blade to maintain its collector value? I presume a new blade will function as well as the original.

Or, if you are restoring these planes to sit on a shelf I don't see how destroying the original blade to make it longer can be called restoring. Seems the blade extension possibilities will substantially lessen the value of the plane and render the blade worthless to a collector.