jaspers

Greeting fellow boaters. I am in the middle of a project and would like some expert opinions and advice. Thanks for all you help in advance. I have a 2004-05 volov penta GXi-F 5.7 block that I have bored .030 over and the bottom end freshened up. This motor was rated at 320 hp when new from vovlo with a 9.4:1 comp ratio and now has around 9.5:1 comp with new pistons. It is a vortec motor with the good 906 casting number 64 cc Vortec heads. The plan was to rebuild this motor and take all the accessories off my 87 5.7 260 Merc and drop it back in my boat. We are also going to install alum intake (vortec) and new carb. (fuel injection on the original Volvo was junk). We are to the point of reinstalling the cam but noticed some pitting and elected to replace instead. The vortec heads have comp cam 1.6 roller tip rockers already installed (should be stock parts). With not knowing the original cam specs here are my questions:
1. Can I reuse the roller lifters, this motor has very few hours on it?
2. What would be a good duration and lift cam to replace the stock cam or slightly better?
3. I have heard many talk about comp cams 256 extreme marine cam but I can’t seem to find that option in a hyd roller, roller cams from comp seem to be much more aggressive.
4. At what point do I need to worry about different valve springs with a cam?
5. Any suggestion on what to run for an intake and carb would be greatly appreciated, somebody has already done this.
6. With the 1.6 rockers how does that effect the cam specs and my choice?

As always, I am trying to stay on a budget and get the most from the least. I want to stick with a marine cam so we don’t need to go down that road. I would be tickled with the new motor if it made between 300-350 hp and gobs of torque so I am not wanting to go too radical.
Regards