Removing Furnace Plenum in 72 Overlander

Hi Folks,



I removed my Suburban furnace without too much trouble, and now I want to remove the plenum that surrounded it. There were 4 small screws into the floor that I've removed, also removed the exhaust as well. For the life of me I cannot find any other bolts or screws holding this in. Any ideas or advice would be greatly appreciated.



Thanks!