That info should be in the holley books. Everyone seems to think there`s some voodoo to those carbs. If you read down the replys you`ll see my signature stating that a Holley tech told me they were the same yrs before. Chipmechanic confirmed what the tech told me. I run a set of 1850-2s on my 63 427 galaxie and it has excellent street manners. I`m running repoped BJ-BKs on my 427 powered 56 F100 and there is a slight difference in manners, the truck has a bigger factory cam than the car. If for some reason you want to run 1850s use -1,-2,-3, The latter ones have been changed, and don`t respond as nicely as the older ones.
