Walker Muffler Co. (big name in exhaust stuff) makes an after market muffler 
for at least the '84-'85 models that is aluminized, lifetime 
warranty (! I think I'll be collecting on this one), fits perfectly 
including metric threaded bolt holes for the mounting flanges, and 
best of all costs about $80 bucks (via Champion Auto Stores).   I've 
had the muffler on about 2 years now and everything looks fine. Our VW 
dealer here in Bemidji found an aftermarket header pipe system that 
they use (meaning it's less expensive for folks) but I can't remember 
the price -receipts at home tho.  I haven't seen any stainless stuff.