[GT182]

It's the curve on the top of the vanes. For all the ones being sold from Cardone, the vanes were shaved flat until they were shown that there is a curve in the originals from Pontiac to match the cruve of the original divider plate. Yes stainless steel plates are sold but they do not match the curve of the originals and cause cavatation of the coolant.... not good and will not help the flow of the coolant. You must pound the living daylights out of the SS rear plate to get a match to the impeller curve and get the correct gap between the plate and impeller. It' close to impossilbe and ends up a mess. Pontiac never made the rear plate so it needed to be pounded on.

Here's a thread I started on the meeting Paul Spotts and I had with Cardone back on 3/3/2011......
http://forums.maxperformanceinc.com/...hlight=Cardone

And go thru this section too....
http://forums.maxperformanceinc.com/...d.php?t=411256

In it you will see the difference in the original steel rear plate Pontiac made versus the new and unimproved SS plates being made now. I personally do NOT recommend them, even tho others have used them and don't mind pounding on them. As long as you keep antifreeze in you cooling system the steel plates will last for years and years. And Inline Tube is selling repos of the original correct divider plates for the 8 bolt waterpumps. Who actually is making them I do not know.

One thing about all the suppliers you have links too..... They don't show a profile of the impeller from the side so you can see if there's a curve to the top of the impeller's vanes or if they are shaved flat. None of the ones you showed are correct just by looking at the number of vanes on the impellers. They're really only crap, and probably made in China. You couldn't give me one of any of them shown. You have to actually have one in-hand to see if it's correct and useable. Photos don't show crap.