very few go by engine hp.. due to laws in the early part of the century in the us.. many manufactors were claiming excessive hp.. so the state of nebraska passed a law that said that all tractors sold in nebraska had to be tested and certified for hp.. they rated the PTO hp and the drawbar hp.. and thus.. this became the international accepted standard..
a ford 2000 in 1965 as sold was 30 hp gas and 36 hp for diesel.. with a 4 spd vrs an 8 spd ..not exactly fair..
in 1970 a gas was 30.58 vrs 31.97 both tested with 6 speed trans so the test were very fair..
in 1972 both tested with an 8 speed and the results were 30.83 vrs 31.19...
so i hope your are less confused... as your tractor may be equipped differently from the tests..
good luck.. Bill