tuning 350

Hi Guys
Greetings from New Zealand. I have recently bought a jet boat running a 350 chev which would not idle and was very difficult to start. Engine has 4150 holley. I found a major vacuum leak which I fixed. I think the timing is also well out. A timing light suggests that the timing is set at 0 degrees (with vacuum advance connected). What should the timing be set at? Do I disconnect the vacuum advance when setting it? Also what is a recommended dwell angle? Engine is still difficult to start when cold. I'm considering a MSD CD ignition box to solve this problem. Apologies for the basic questions- any assistance would be greatly appreciated.