Yes the fan shroud will hit on the bump out. You might be able to cut out part of the bump out to make it work though. I didn't think the extra inch or two was worth messing with so I went with the flat firewall.
I have have been running my 503 for 24 years now. Dual carb, dual ignition. I switched to mixed gas. The oil injection was a pain in the ass. Burning 5 gallons a hour at 5950 rpm. Cruises 69 mph. As light as you are it should do pretty good if your airplane is light. My Bandit started at 456lbs, but now is around 485 or so. I am using a 3 blade ground adjustable 66" ivo prop. I am thinking the 582 is the same mount as the 503. Does anybody else know for sure?