You are going to have to go marine and most times yes the price goes up but there are reasons for that for one you need to use marine carbs alternators starters etc for safety reasons for one they are designed for a closed environment and the posssibility of fumes etc they are made explosion proof for the starter and alternator so there are no sparks. Dont skimp and use auto parts except for things like gaskets and standard parts. Now as far as where you can get a new cam for the end of the cam I would try Robert Henkel at
http://www.chris-craft-parts.com phone is 810-748-3600 or you can try Earl in Harrisson Twp Michigan at
http://www.marine-sales.com/ phone is 586-468-0937
and there is Danny Cook down in southern Ohio but I don't have his number someone else here on the forum will though.