About six months ago we called every overhaul outfit listed in trade-a-plane, internet searches, friends of friends and Continental Motors. Definitely post any shop that is interested in overhauling the Continental C-?? engines.
One outfit offered to overhaul the C-85 but, told us they are going to charge for tear-down and inspection before they order us a new O-200.
Ask Continental if they'll give core value of a C-?? engine in exchange for an O-200. They hinted that they may be accepting E-??? and C-?? as cores.