So, I have discovered a third manufacturer of the Centurion-type van conversion, they were called Van-Truk, Inc. I saw the truck back at the 4th of July, took some pics of it on my Iphone and just never got around to posting them. Anyways, someone on another forum was looking for a van-truck conversion on the east coast and I sent him the phone number. I ended up going out to look at the truck for him. He's now on this forum, his name is HAB.
Anywho, I talked to the owner a little and he made some copies for me of the paperwork he had on the truck. I'll see if I can get them scanned and on here in the next week or two, but I thought I would share. The truck in question is this one:

Here's what I know:
It was purchased by a James Cash from Texas from Van-truk, Inc. out of Ft. Myers, Florida on 8/16/85. The only thing listed, aside from color selections was a "Front bumper guard" and the purchase price was $23,845. It was shipped to Texas to Mr. Cash and according to the present owner, Mr. Cash owned it until he passed away, his wife sold it to the present owner's brother-in-law and when he passed away, the present owner got it. The vin is 1FTJE3411FHB55807 and it's an 85 "Van-Truk III" with a 6.9 in it. Truck currently only has 130K miles on it.
I get the impression Van-Truk, Inc was a small operation as the president, Mr. Wayne Newton (yes I'm serious) was also the "salesman" listed on one of the invoices and his signature is on a couple of the pages.
Anyways, that's about all there is to go by, I was hoping for a sales brochure but he didn't have any. Like I said, I'll try to post up what I have but I thought I'd share it with everyone since it seems these are even harder to find then the Cabriolets and Centurion conversions.