Help me pick a carb for my 20
 

Dudes:

https://i.imgur.com/7hU7Vsh.jpg

20' Sleekcraft Aristocrat Twin Tunnel w Alpha outdrive and a quicksilver prop, forget the specs, maybe 23"?

Mild 350, .30 over, weind xlerator intake, not sure the cam specs, and Stellings headers,Gear drive.

It currently has a Holley 1650-5 650cfm carb on it, and it's been excellent but it's starting to leak fuel. It's also boring looking and sort of ugly; I have an exposed engine so I want to get something polished. I used Holley's carb selector, and it wound up giving my a 600cfm 1850-S (polished), or a Demon 625cfm.

Questions:

1. Mechanical or vacuum secondaries? Why?

2. Is 600-625CFM correct for my application? The carb selector is probably for cars so I'm not sure how the loads of a boat would differ than a car.

3. Demon vs regular Holley: Thoughts?