Thanks for all your input, folks.
So - I rigged things up this weekend... pictures below of what I came up with. I'll be trimming the vinyl dryer ducting a little shorter - this was a 16' piece it came with - tested well yesterday seems like it should keep things pretty cool.
Not sure if any type of exhausting is possible/needed- nor how i'd even do it. I figure i'll crack my roof vent if needed to release humidity.
First I just zipped 6 screws to the face of the metal piece i found (10" long by 3" wide-ish). Then i wrapped it with the aluminum tape to make it air tight to the unit (not pictured.
Then i took the 6" exit off the unit down to 4" in order to get dryer duct connected. Had to use a 6 to 5" metal reducer, then a 5" to 4" PVC reducer since that was all the hardware store had in stock. Again - i plan to trim the white hose so the air has less distance to travel to get inside the van.
I cut a piece of plexiglass that fits in the top 1/3 of the window tracks on the sides, and closing the window below it puts a little pressure on the plexi tight enough for me. Zipped a 4" hole in the plexi & mounted a toilet flange to it. Just one screw will take the hose clamp / venting off the flange, so it should pack up fairly compact. Plus I can use it on my '75 as well.
I'll probably build a little 'roof' (or use a bin lid lol) to keep the water out from inside the AC unit in case it rains. I plan to give this a whirl next week at the Nats.