You mean M3's? I know the M3 stuart light tank were sometimes outfited with "tusks" as you say, welded to their chassis, again, as you say, for flattening hedgerows. And if that is what you are talking about, then you should know that the M3's had a 37mm cannon if I am correct, and would probably be about the same as our scout car. So if the 37mm on our armored car can kill the tanks in the game from infront then OK.
Stuart was also noted as the Light Tank M5. M5's were fitted with "tusks", as were the Shermans.
Tiger I had a Kwk 36 L/56Tiger II had a Kwk 43 L/71The Nashorn had the longer gun used on the Tiger II.
To call these two guns the same . Is like calling the 75 mm fitted to a M4 Sherman and that fitted to a Mk. V Panther the same thing . The M5 Stuart was a redesigned M3 Stuart ,was redesigned primarily to remove shot traps .