Here’s a picture of gen IV and brackets
First view is looking at unit from back side (toward dash) blower on the right,ac ducts left,defrost ducts center left.
Next view is parts that come with universal evap,note the brackets (lower right) large bracket mounts unit to firewall,smaller bracket to dash.
Additional parts needed inside cab will be defrost duct (defrost ducts supplied are not long enough), must use Vintage Air controls to operate unit 79 era can use 3 knob/lever (must use some kind of plate over oem heater controls) or 86-91 oem head can be modified with cable converters.
Easy way for AC vents is to buy the underdash vent system from VA (can be painted to match dash), in my truck we used small aluminum vents and made a plenum to conect duct hoses, if I had the chance to do it again would have welded extension to bottom of dash for larger ac vents.
Last is lines and hoses which is the tough part,your going to have to patch holes in firewall by welding them up or bolting in metal plates, aluminum 4 port bulkheads look cool on a clean firewall but are a real challenge because of limited space to make 90 degree turns from heater out/inlets to bulkhead,ac lines can go out oem hole in firewall.
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