Now you have something else to keep looking for in Western Canada, this together with a stove for John will keep you away from your house rebuild for a while.
Anyway this conversion on the M-H 20-30 was four pieces,
1. Cast Iron exhaust elbow
2. Alliminium tube with flanges for manifold to carb
3. Robin carburetor (think they are same as a Zenith?)
4. Alliminum flange carb to aircleaner
I still have all these parts on my shelf somewhere, just can't remember if the carb actually had Robin cast into it or not, but seem to remember the alliminium tube did.
Maybe when you are next over here you could take these parts back in your suitcase?? I am sure you have a tractor which could use them in your bone yard.