Still digesting your post.
Can I use my original metering plate and bowl on the new baseplate and airhorn? The metering plates are both stamped 6293.
Sounds like the throttle bodies are the same type then, you may just get away with this 'Mix & Match' after all!
You should only have ONE metering plate, and one metering block.
(Block Front, for power valve and jets, ect.
There shouldn't be one in the back, it should be just a metering plate screwed onto the venturi body,
But I can't tell for sure until you give me the LIST NUMBER off the choke horn so I can look up the stock parts it's 'Supposed' to have.