These amplifiers need to be converted at the factory. The conversion consisted of a mono driver doard, a new backplate that contained only a single hole for an XLR input and a single rca connection.
It is definately worth a phone call to see if they can do this, but dont be disapointed if they do not have the back plates in stock.
If not sell the pair of 80's and buy a pair of 160's, here on Audiogon.