1bbl slant pics

I also suspect the mysterious "2nd hole" is for a "feedback solenoid". Those were used on cars starting in the 1980's until "fuel injection" started. I think all of Chrysler's were with the "lean burn" system. My 82 Aries had that (termed "spark computer"), but I don't recall the feedback carb was a Holley 1945. Try looking up the PN to see what engines it was used on. Perhaps slants in Aspen/Volare, Dodge trucks or vans. I don't know if you could even use it without the solenoid. I recall a Holley carb book from then that described how they worked. It looks like the solenoid controlled an air bleed.