I figured out part of the mystery. The Mixture Control Valve was only on carbs for manual transmissions, and the new carb came from a Raider that had an automatic. Reading up on it, it isn't required. Its just an emissions thing to lean out the mixture between shifts. I looked at the Montero manual instead of the Raider manual and it explained what it is for and how it works. Looks like I'll be bolting that carb on when I have the time. Thanks so much to everyone for their help in this, I really appreciate all the feedback and information.

1987 Raider, 346K miles and going strong -31" tires, otherwise stock.
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