I took the old blades in to the local repair shop today and they are monsters. Very heavy duty and appear to have once been 18" made from very hard 1/4" steel with a 7/8 hole. Unfortunately no one seems to make anything much less stock anything like that so I bought a set of Scag 18" blades and took them to a machine shop to open the center hole from 5/8" to 7/8". Thanks again for the help.
Onward and upward....