500 HP is definitely in the realm of any big block. Obviously even more if the engine combination is up to par. I would say 600's are MINIMUM. If you have the bowl off of the pump, the impeller should be stamped as to what it is. Assuming you are just looking at it from the intake of the pump, it would be impossible to tell, on my Jacuzzi pump, it is stamped on the ID tag what impeller it originally came with. I would say it has ans A or B impeller. Stainless is about a 1000 dollars, and everyone tells me 6000 rpm and 600HP is the max for an aluminum impeller. Pumps are supposed to suck from 6 feet, so watch the sand bars. haha.
[This message has been edited by wsuwrhr (edited September 18, 2000).]