rear heater/ac in '90 burb needs help

I got this '90 chevy, 1/2 ton, 4x4 suburban and the rear heater/ac fell off the ceiling! The unit still works fine but the housing for it is all broke and the motor/blower/core or whatever you want to call it is not mounted to the ceiling. The way they made it, it just kinda rested in the plastic housing. The housing,which is part of the interior trim, was screwed into the ceiling but the motor,which is pretty heavy to not have had any kinda support, is too heavy for the plastic housing and after a few trips down a bumpy road, the whole thing just fell of the ceiling. I could try to buy a new plastic housing piece, but it seems kinda pointless since I gotta drive down bumpy dirt roads a lot for my job, and the weight of the motor or core will just break it again. There is no place to mount for keeping the weight off the plastic housing unless I want to drill holes in the roof. At least I can't think of anything. Right now I got this wooden frame built to hold it all up from underneath which works pretty well untill the time comes for me to have to use my spare tire and then I gotta dismantle the whole wooden frame that I built. I thought about just doing away with the heater/ac back there completely but my crew has to ride back there and it gets pretty cold while the people up front roast so I gotta have it. I just can't believe whoever designed it was expecting that plastic trim to support all of the weight of it. :banghead: :crying: Has anybody else had this problem and how did you fix it? Any ideas? :eek7: