Yes, the 4-speed is the 4R100, which is based on the E4OD architecture, just with some improvements for key components, and a smarter electronic valve body.
I initially used the Tru-Cool thermostat with mine, but it didn't work right. It let it get WAY too hit before opening, and I had to remove it in a parking lot the first trip with the trailer, before I roasted things. Now that the van is used mostly for towing duty, its fine without out. When I was daily driving it, I had to block the grill in winter to get the trans up to temp.
