Old Peugeots are a Cul de Sac the standards are applicable Only to France at that time

where the rest of the Planet uses 1" Tube , 25.4 they wanted 25.0,, a 9/8" Tube is 28.0mm not 28.6 New FDs dont fit without shims

And so you have 22.0 mm stems when the rest of the Planet used 22.2mm 7/8"


if you insist , braze in a Long Gusset in the back of the fork to resist the disc forces wanting to straighten out the bend

and Put in Lawyer Lip Dropouts . as once the disc is Grabbed by the caliper the torque axis is the brake pads , and the wheel wants to come Out of the dropout
or remove the dropout and put them in opposite sides so the dropout opening is facing the Front , not DOWN.

Or maybe put the caliper on the front of the right fork blade , then the same torque center rotation, pushes the axle into the dropout rather than Out of it.