I recommend two Dangerden waterblocks hooked up to an Eheim pump and a Chevette heater core. Use 1/2" silicone tubing. Use ducting to space two of 120mm fans 1" away from the heatercore surface (keeping all the airflow going through the heatercore). Have the fans blowing into the heatercore.
Waterblocks -
www.dangerden.com
Eheim pump - search the web on
www.google.com
Chevette heatercore -
www.autozone.com or local source of auto parts
Silicone Tubing - medical supply store or
www.caseetc.com
Fans - just about anywhere, but
www.caseetc.com has a bunch
Oh, for the heatercore, just use JB-Weld epoxy to add some brass barbed 1/2NPT fittings into the heatercore input/output tubes.
For the water, use Water Wetter(tm) and only Water Wetter for an anti-corrosion agent.
There, that just about sums up most of the recent conclusions about watercooling. Everything else is just for making it quiet or is the mounting details.