Yeah, I have to tear into my Zenith again to ascertain why she's running on the rich side too.
I'm not familiar with the stromberg, but the next thing I'm going to check is to verify that my choke is closing an opening completely. I have a feeling that the choke butterfly isn't opening completely when the choke is all the way off.
I've fiddled with the idle mixture screw, so that seems ok...
So, what is your choke situation?
Current Rover Fleet:
1996 D1 120k (finally on the road)
1970 IIa 88" (the running one)
1970 IIa 88" (parts truck - need any parts?)
1966 IIa 109" (next project...)