I found these photos on a Corvair fan site today. It's not what I thought it was going to look like, but it's definitely a Hot Wheels!
That flat six cylinder will make for some interesting customs, but the fan belt is wrong, they wrapped up the front and across the top of the engines in a 90 degree bend.
For anyone not familiar with these vans, they also came in a pickup version. Here is a link that shows a "normal" window van: