removing the heater and cabinet from a 70 Overlander

[rayandre]

So I'm replacing the original Suburban with an Olympian. The furnace came out easily but the cabinet seems to be stuck. I've removed the ducting from the plenum, removed screws holding the plenum to the floor and I see no mounting screws attached through the exterior to the frame of this cabinet. I can see the two vents and see outside but no rivets or screws. It wiggles a little but something is keeping it from coming out. Any ideas? I'm very close to just taking acutter to it and cutting it out!