Those images look too small to decipher.

Here's my advice (you are welcome to continue to ignore it of course) -- ask him for a part number on the pump he wants to use. Make him make the decisions and tell you what to buy. He's the expert (*cough*)

A "bravo" pump is probably driven off the crank and I doubt you have room for that on your engine. That is why the raw water pumps for inboards are mounted on a bracket and driven off of a belt. Any chance you can go down there and take some photos? I'm very familiar with 460 engines but not familiar with the marine application for them. At $4000 in you could have easily swapped in an EFI big block engine at this point.