When I purchased my 02 v92c it had a solo mustang seat, with a solo bracket to attache the seat where the passenger seat had attached. The former owner had chrome plugs in the three holes where the passenger seat was attached to the fender
corbin sells a solo seat (just ordered one) that comes with a bracket that bolts to the top swingarm brackets under the front seat. I allows you to bolt the solo on to its own bracket. Expensive, but they make a good custom seat and mustang doesn't offer the bracket with their seats.