I finally got around to disassembling the exhaust system of the bus, with the intention of boiling out and refurbishing the heat exchangers. It took me two beers and a few hours of squirming underneath the bus to get the (really) tight bolts out of the way and I got the muffler and exhaust system out eventually, sans three bolts. I dropped off the pipes at this place called L&M Stripping, which will strip out the rust, gunk, and the burnt oil residue that coats the inner walls of the heater boxes that my lucky passengers are inhaling if I choose to operate the heater. Hopefully it goes well. The next stop is getting them hi-temp ceramic coated. I'm scurred of putting everything back together, especially from what I read about exhaust leaks. I don't really know my way around cars - with the Bentley guide as my bible, I just hacked at it with my socket wrench and put my faith in bahala na si Batman. Hopefully it goes well!