On a Durst 138, you would need to fashion some type of alternative negative carrier since the negla 138 would not accomodate the thickness of glass plates...at least that is true of mine.

Beyond that, these are great enlargers...

I agree that the images that you mention probably have some historical significance. If I were you, I would impress on the owner of the negatives that a fiber print would enable these to last for an optimum period of time.

Good luck.