Ok, that works. Here's some more helpful info:
Here's a closer shot of the solenoid. You can se the 9/16" hexagonal end for a wrench to turn it for initial idle speed. Inside it you can see the 1/8" hex screw to stick an Allen wrench inside the tip. To set the base idle speed, hold the solenoid with the 9/16" wrench and use the 1/8" Allen wrench to turn the screw until it seats all the way. Then pull the plug to the left of it while the engine is idling. Back off the hex screw with the 1/8" Allen wrench until you hit the recommended base idle speed. Reconnect the wire and recheck you base idle speed to make sure it hasn't changed.
Emissions diagram on the 49 state 1978 250cid. I'm not sure how different yours is from this. My comments I added to this are for a Holley-390cfm/Offy/Stovebolt swap. The goal of keeping the EVAP, PCV, and vacuum advance after the swap (even the Thermac air cleaner too if wanted).
Here's a labeled pic on how everything is attaches to the carb.
