One thing I am finding is the cost of AFB tuning parts. 15 bucks for jets, 13 for metering rods, 45 bucks for accelerator pump nozzles, fine tuning adds up.
I rebuilt my column a while back and I don't remember any plate being 1/2 to 5/8 thick. The retaining plate shown in the repair manual is around 1/8" thick.
Only the original engine is code correct. Some will use the term date correct, I don't know why that makes a difference personally. I guess it makes some people feel better.