It seems to me that OTT FD routing was a standard term used in the bicycle industry and didn't have any issues reading that it was over the top of the BB rather than OTB. One would have to assume the OP was a complete idiot to read it as a top-pull routing.

Easiest thing to do would be to just slide the cable through the cable stop. It doesn't look like it is threaded for a barrel adjuster so even if it didn't line up 100% perfectly with the braze-on or bolt-on OTT cable-guide it shouldn't cause much friction on the cable. The amount of friction on the cable guide will be orders of magnitude more friction so any misalignment of the integrated cable stop would be inconsequential -especially in a friction-shift setup, which I will assume the OP is going with probably, using this ancient FD. I don't think it would be an issue with an indexed system either, if the FD's pull is compatible.

If the OP is worried about chaffing on the cable as it rubs the stop with a more radical angle, a little bit of smoothing with a needle file or a taper reamer should fix that easily.