Late 1970's RER Drive Disc Removal

Hi folks, I'm in the process of replacing the tired and smokey B&S on my late 70's Rear Engine Rider. I haven't bought the new engine yet but I'm satisfied with the responses to another post on this site that I should have no trouble getting one that will bolt right up. I removed the old engine this evening and have it completely off of the mower now. I'm having trouble removing the aluminum (?) drive disk from the old engine's crankshaft. The disk is held keyed onto the shaft and held with 2 set screws which I have removed. I've sprayed it down with some penetrating oil for the time being and have GENTLY tapped it a bit with a rubber mallet but it seems too delicate to really whack. I wanted to ask if there is any trick to getting this piece off the old crankshaft and onto the new engine (maybe a little heat from a torch would help?). Thanks







Cap'n can't mow at the moment.