Sounds like an older motor, my opinion, buy the cam kit with springs, make sure you have room for the higher lift, that you're not going to hit the guides. Maybe even replace the valve seals while you're in there.

You aren't going to want to hear what I am going to say, but if it was running good before I would leave it alone and enjoy the boat for what it is. How many hours are on it? Going back to another flat tappet cam can be risky with some of the issues people are having with lobes going flat, and I see very little gain to be had with a 305. Save your money for beer, or if you really want to see a difference, save it up for a 383 or even a 350. The small bores and poor heads on a 305 are never going to make any serious power. I tried building up a 305 as a teenager in a Camaro many years ago - headers, decent intake, Holley carb, better cam, etc. Best I was able to do was to get close to what a stock 350 would make. Sorry to be a Debbie Downer, but that's just my opinion. Good luck with it which ever direction you choose to go.

The motor only has 240 hrs on it and it's in great health for its age. So getting rid of it for another sbc is hard to do. I'd really love to build a 383, but only if this one was ready to calf out. It has the gm factory H.O heads on it so that's a plus. I'm aware of the lobe issues hence I run shell rotella diesel oil in it. it's loaded with zinc. I'm just looking to liven her up a little more, and a cam kit isn't that expensive... The boats did 60 mph+ with stock Volvo aq271's (350 ci) which is what I'm aiming for.

You might want to figure out exactly what you have so you don't go the wrong direction. Like you said it's not that expensive, give it a shot.

What kind of boat and size are we talking about?

It's a Baretta Phaser 230 cuddy. 22.5 ft long weighing empty around 2900 lbs

I did a FT cam in a 350. I used a TON of Crane assembly grease on the lobes and lifters, Comp assembly lube on the journals and Comp break in oil in the pan. I ran the engine for 1/2 hour between 2000 and 3000 rpm. Then dumped the oil. It's running strong now with no issues.