The 1974 Thiokol Imp V4 Ford that I rebuilt had a Solex Carb that was heated by engine coolant. The carb kit was one of the hardest repair parts kits to find. I did find a NAPA kit for part of the carb overhaul. Had to fabricate other parts like an accelerator pump, and some gaskets as I recall. The carb overhaul, new fuel lines, filters, along with a new fuel pump really brought that engine to life.
Seems these older carbs and fuel sytems gum up and the engine will lose a lot of HP and will not function properly with old gas left in the system over the years. Northern Engine in MN has some of the Industrial V4 Ford parts that I needed.
Parts are a bit pricey, but that is the penalty we pay to play.
I had many of the NAPA part numbers listed in the Thiokol manuel that I gave to the new owner when I sold the unit last spring. If necessary I can probably contact the new owner and get many of the NAPA numbers for repair parts that I entered in the manuel. Let me know if you have a parts problem and I will see what I can do. From what I could find out the Saab basic engine was the same, but the electrical and fuel components never seemed to match up on the Imp engine configuration. Overhaul gasket set came from NAPA and I believe it was listed under agriculture equipment possibly New Holland.
As to the lead issue, I agree with Pixie. Ignorance is bliss. Never seemed to be a major issue.