Front brake wont work since he is running dual brakes, no? Brazing on new mounts would be a solution, but that might be another hassle by itself.
Given you're running quite slim tyres, you might fit a 26" wheel with a skinny tyre into a 24" MTB fork. 26" rim == 559mm diameter, 24" rim = 507mm diameter.
For a 1.5" slick you'll probably need 40mm+ between the rim and the fork., so that's 320mm from skewer to tread.
Front brake wont work since he is running dual brakes, no? Brazing on new mounts would be a solution, but that might be another hassle by itself.