Here is what I would do if I had to replace my metal tubing from back to
front in my Vanagon.  Remove your old tubes.  Go to the local muffler shop.
Get them to bend you some new ones out of steel (or maybe aluminized steel
would be better).  They could put a bead on each end with a mig welder.
Cheaper, faster, (maybe better) than getting these from the dealer.

Other opinions welcome,
Ken Wilford
http://www.vanagain.com
John 3:16
Phone: (856)-765-1583
Shop:   (856)-327-0027
Fax:     (856)-327-2242