Do Not Use Steel Coolant Pipes.
There is a real good reason why VW went to the plastic pipes!  You can easily find, from many of our friendly vendors. conversion packages that make this possible and easy to do.  The steel pipes will just rust out again and leave you with the same problem if you plan on keeping your Vanagon.

I've had SS pipes on my van for 4 years, here in the Rocky Mountain Region, where we get, and I drive in,
snow, ice, slushy roads. There is no sign of rust or other corrosion on the pipes to this point. It's a very good
way to go and the sectioned pipes are a relatively easy installation.
If you want OE rubber then Van Cafe has everything you will need:
http://www.van-cafe.com/home/van/listitems_1141_18?
So does Go Westy:
http://www.gowesty.com/ec_search_results.php?search_phrase=coolant+pipes
Notice their SS set up as well:
http://www.gowesty.com/ec_view_details.php?id=4407&category_id=&category_parent_id=
I went to bus depot's site and found what they offer for my '87:
http://www.busdepot.com/radiator-cooling-system?q=All&type=2&model=23&year=408&variation=146&category=1160
Guess where you live might influence which of our usual vendors might be the best?

bob