Normally, imperial diameter propshafts would have a 12:1 taper and metric shafts a 10:1. Be careful though, adaptions and odd taper sizes do crop up surprisingly often - taking the prop off and measuring (accurately) would be advisable.
Only definite way to know would be to measure the shaft. Either that you have to be convinced that the shaft is original and the data received from here or from Hunter is correct.