1978 Excalibur winter to do list
 

So purchased this boat in the end of July. Used it about 35 hrs with no failures. Had a blast with it but like all boats has minor things to address so this winter I am pulling the motors to deal with some minor leaks. The deck is being repainted and thought I’d take some weight out of it with aluminum exhaust manifolds, intake manifold and possibly aluminum heads. I may do a cam and lifter upgrade . It already has good roller rockers. What can I realistically expect in performance if I’m making a true 425 hp. I want to keep it super reliable and economical so I don’t really want more power than that. Only used 1500 dollars of fuel in 35 hrs of use most of which was cruising around at 42 mph

Sounds like that was an excellent purchase!
I installed Holley Sniper EFI on mine and loved the results
I can't help with possible performance improvements
But, if you are looking for used parts Sick Stinger is an excellent source and great guy to deal with. If you want new Diamond Performance on here is excellent as well.
Good luck and post your progress, its a long winter up here!

Did the efi help in all aspects ? Did you need to install o2 sensors?

1978 Excalibur winter to do list
 

I was wondering how your updates turned out?