I've found a really cheap bypass regulator like this one, and was wondering how it would work using it for regulating water going to the engine. It's made for gas/alcohol/diesel so I would assume water wouldn't hurt it. 10AN inlet and outlet with a 6AN bypass outlet...just a thought since I can get one for next to nothing.
http://static.summitracing.com/globa...ei-13114_w.jpg
for what yuor wanting to do, you can buy a cheap brass water pressure regulator for a water well and use it, they're adjustable and do the same thing as the high $$$ kits, and they're made to see alot of water going thru them.i got one for my project tx-19 for @20bucks at the local plumbing store, painted it alum high temp and it looks fine.