Re: Anyone know what this TH400 is from?
It is not a shevolay. I am 100% certain of that. I have one of those under the Jeeplab bench #1 and jus looked at it to confirm. It is NOT shevolay.
I am 90% certain that it is NOT BOP. That stands for Buick, Olds, Ponticac. They all used the same case back in the old days. The BOP, IIRC, is scooped out on the top and has a different bolt pattern and measuements and also has the starter on the other side than the shevolay. So that part is similar at least.
I would guess that it is a Cadillac model. There are less of them around of course and that may be why it is not easily recognized.
Regardless of that, though, it probably is worth exactly nothing at all. It is weathered, has no matching interior components and is probably in that condition for a very good reason. (It is broke/cracked/tweaked/leaks/??????)
By the way, it could also be a Rolls Royce. Yes, the auto in the Rolls and Aston Martins was a TH400. May still be for all I know. There used to be a lot of GM parts in Rolls Royce products.