There is no 800hp marine cam for a mechanical engine. The 580hp marine C models uses the 0r3787 and as well as the 587hp generator set engines that the 10r1439 cylinder pack comes from.
Have your C model pump built so you can use the actual matching 0r8789(65% more fuel then a 3421) nozzle that comes in those engines.
Use pump cam 4p-0990, this is a pump cam that works in your C housing with your barrels and plungers that will allow you to use your 7FB timing advance and also has timing specs like the 24* pump cam used in the 7FB.
When the cams were changed from the 0R3013 to the 0R3787 this is the information that came out along with it.