I am designing a new higher flow water pump impeller for the 250R. It will be based off the same mounting design as the 89 impeller. Here is some pics of what it may look like.
impeller 1.JPGimpeller 2.JPGimpeller 3.JPG

I don't know how much better it will be until I test it. I won't sell any of them until I have confirmed a higher flow and to what percentage. They will be made out of 6061-T6 aluminum I'm not sure what they will cost yet either. It will partly depend on how many are made. Rest assured, they will be as cheap as possible. Also keep in mind that you will have to use an 89 style water pump shaft in order to use this impeller since it is modeled after the 89 mounting style. The 86-88 shafts and impellers have splines, and the 89 style does not. I'm not looking for commitments, just ones that would be seriously interested.