Looks to me that there were more issues, the residue on the pistons are from excessive oil coming by the rings. I believe you said there was oil all over the rear and had to add. The cam looks to have some wear. Sure is a mess for 6000.00. The bores are all scored, the heads show excess oil. 3/8 fuel line never did that damage.

Lowest point of the cam and use wheel bearing grease not multi

Too bad I am so far away, however any CC, Malibu,Mastercraft dealer scould all the parts you need. 351 Windsors were very common in Ski towboats..

They also have a 25 lb flow vave in the plumbing depot  $ app 6.00 seems to work well.

Did you use the center metal valley tray gasket? It takes up space that obvious you have, not only vacumn leaks but throws oil out everywhere.

Check for vacunm leaks and set the corner screws in and the out to 1 1/2 turns out. Be sure the air bleeds are clear, spray them with wd 40.

Marine dist, alternators,starters are enclosed for spark explosion and carburators have a J tube in lieu of vent tubes. Electric fuel pump have saftey switch shut down .Now that is necessary for enclosed engine compartmants. Most ,if not all , open cockpit use only automotive equipment.

I was a Freshman in high school my buddy Jimmy Leblanc  and Jimmy Hurtubise built a 9 ft pram put a Evevrude on it. Still have a picture with Jim driving it, we used to share. Jim went driving race car and I went race boats.

Your right I do have that switch on mine.

I have it as close to the tank before the fuel pump. It is a Carter 112 GPH pump that runs when the ign is turned on. I use the Marine version at Summit $ 69.00, been runing the pump for the last5 years no problem.

I have a pair for the engine to stringer, they are heavy.

I myself use both, the electric keeps the prime up, no start troubles.

Just get to run twist give it more to smooth out. You want your total to be at 2500 -3000 rpm. The inital will be what it is at idle. The total is what you after, each dist springs will vary.