I couldn't find one, but I do purchase machined parts daily. And looking at this thing, it wouldn't be cheap to make. The water pump housing is $165, so I'm thinking the thermostat housing would be similar.

I sent pics to another forum member with a housing for a 300D. I'll see if he thinks they are the same or not.

There is no need to "seal" the bolt. The bolts are outside the perimeter of the gasket. On my 300D, the bolt holes are open on the back side already. It's just a matter of whether the bolt threads into the housing or into a nut behind the housing.

I would just...
 

Strip one from a wrecked engine. they are so much more plentiful than trying to fabricate one.

That's the plan. It's why I'm trying to determine if one off a 300D will work incase I can't find an SD at the yard.

I'm pretty sure...
 

...it will, as I recall it working when I was shifting parts from my 1985 300D engine to the 1983 300SD engine that was to be put in the 1985 300D body. While there were a surprising number of differences between the two, I don't recall any difficulty with the thermostat housing or connections to it.

they are the same
 

To answer the question, they are the same. I just put in a housing from a 300D that I got from a fellow forum member. Now I have to see if the new thermostat helps my car run a little cooler. Still can't figure out the jumping guage though...

Try replacing the negative battery cable. I got about a 75% improvement on 2 123's by doing that.

i agree. thanks for clarifying my muddled thought.

tom w