So I picked up this Jim Redcay frame/fork last week and I'm starting the re-build. Anyway, it's a cool old frame with beautiful detail and I'm not gonna complain about 27" wheels but I can't figure out what to do with the rear brakes:

First of all, the braze-ons are inside the rear triangle - which I suppose shouldn't make a bit of difference since front brakes are mounted forward anyway, but instead of mounting the braze-ons facing inward, they are mounted outward. As a result, the fork canti posts are spaced 58mm center-to-center, but the rear canti posts are 90mm center-to-center.
Is this a set-up I should know about?
What brake am I supposed to use in the rear?
I am hoping to mount original Mafac cantis on it (if I can find an affordable set) but when I tried an old set of Shimano deore's to see how they strike the rim the pads would have to be way out toward the ends of their posts to strike right. Does this seem odd to anyone? Is it possible this was meant for some sort of U-brake? A mafac centerpull mounted from the side pivots rather than the center-bolt? Or am I just making too much of this?
From what I've read, Jim Redcay didn't mess around, so what did he intend?
In any case, if anyone has any ideas - or better yet - if anyone has the actual brakes, let me know.