I ended up going with RBC. Try them. I just got my CB750 1981 this past weekend.
I tried Intact, Desjardin, Riders Plus, Allstate, Dalton Timmis, RBC, Statefarm, Echelon
Statefarm was the highest.
Dalton Timmis was the 2nd lowest but only with the vintage program, but they must do an appraisal...