Universal AC evaporator

[truckin 79]

Well I have spent about a good 3-4 years trying to install AC into my heat only 79 Truck. I thought I finally achieved success this year but a leak in used evaporator has me thinking of new ideas. I used an old ARA part that was oblong and fit tucked inder the defrost vents. Everything else that I have put on truck to install AC is new. Has anyone tried using one of these universal AC evaporators? On ebay it is like 90. They dimensions are 16" wide, 13" deep and 6" high. I am thinking if I can put evaporator under dash at a slight angle is should work out fine.