marine carb on a duster 360?

I am currently in the process of rebuilding my 360. The engine builder said a 750dp would be a good choice. A guy at work gave me a carb for free and said he didnt know if it was a 750 or an 850. I looked up the list number and it is a 750 holley for marine use. Question is whats the difference and has anyone tried this and have input?