Merv
I did some looking around for a similar setup and also had difficulty finding a ribbed water pump pulley. Eventually, I dug this up from the March website and subsequently found the two sets for sale on the Summit site.
March Catalog
http://www.marchperf.com/pg35.html
Underdrive crank
http://www.summitracing.com/search/?...y%201670&dds=1
Standard drive crank
http://www.summitracing.com/parts/MCH-1675/
These both rely on using the standard drive water pump.
Let me know if you look like ordering a set as I have been thinking of doing this for a while and we might be able to share the postage.
Cheers
Geof