I have an air/water intercooler setup in my AAZ Vanagon.
It's a bit tough to find an air/water intercooler kit second hand, which is the only way the price can be kept reasonable.
I bought my intercooler & radiator second-hand from one of the GMC Syclone/Typhoon guys. I then adapted it to the AAZ Vanagon. Most of those Sy/Ty guys are switching to air-air intercoolers, so they are selling their factory setups. Frankly, if I had a front-engined VW (like you do), then I would be doing air/air, too.
It's fussy to set up, more expensive, and more things to go wrong. That said, I suspect it is more efficient than the air/air intercoolers mounted in the bottom of Vanagon rear air ducts... Luckypabst sure didn't have a lot of luck with mounting his air/oil cooler there anyway...
http://vwdiesel.net/phpBB/viewtopic.php?t=13579&postdays=0&postorder=asc&start=105I have 2 water pumps, front and rear, run by relays that switch on as soon as the alternator gives a charging signal. Probably this is overkill, and I could get away with just 1 pump (but there are 300 miles of rad hose in the rear-engine setup).
I can look up what I'm running (can't remember off the top of my head), but I can't claim either pump as the best for the purpose. The bigger of my 2 pumps is a Jabsco marine unit, and it was ungodly expensive. You need high flow rate and the capacity to run high temperature fluids. Not an easy life for an electric pump, and if you're not prepared to $hell out for a good one, you should really stick to air/air intercooling.
I recommend that you ask around at the Sy/Ty forums. They have a fair bit of collective experience with air/water intercooler issues, deciding which pumps suit the purpose best, etc.
http://www.syty.net/forums/index.php