Ah yes, the bike is in fact a 6 speed aluminum. A Univega Viva Tech a budget version of the popular steel Viva Sport, circa 1989 (or so the internet tells me). The brake issue I was aware of. I have side pull calipers, they may even fit 650B as they are adjusted all the way to the top at the moment and if not I suspect finding ones that fit should not be difficult given the position of the stay.
I may just go for it spread it myself.