The heater guru in Colorado is:

J.B. Heaters
2162 Vineyard
Castle Rock, CO 80104

303-660-9032

One other post described the owner (Joe Boerico) as a "jerk."  He may be.
I'm not interested in a flame war over him but he was courteous to me over the 
phone, fixed my unit at the agreed on price and in a competent manner after 
answering several of my questions.  He's not cheap but he gives good value 
and quality for what he charges.  If someone else had a negative 
experience, then I'm sorry for them because I've been in their shoes and 
its no fun.  In any event, I suggest you call him before cutting anything 
in any bus.  He may be rude to you or he may save you from doing harm to your 
vehicle.

Skip Correll
Chattanooga, Tn
72 Westy, 73 Thing, 72 Super Beetle