I would think the easiest way to install an evaporator would be to grab a heater/ac box out of a common vehicle that meets your specs and swap it over. My father (Beaubeau) and I used a Dodge Ram unit in his International Eagle cab for a project he's doing (not MV related) and it wasn't hard at all, and that was a really large unit. There are much smaller, but still efficient, boxes that would fit in a fairly small place, up under the passenger side of the firewall. Hook up 4 hoses and you are almost done. Run ducts to blower vents that you can put where you want. Hardest part is a 24v fan.
What does the m1008 use...is the fan 24v? If so, maybe use a generic GM heater and AC box, and use the M1008 blower. This would be especially useful for those who don't have heat installed yet.
Jim