That idle solenoid may have been on the car, but it is hardle likely that it was original. Look on the
Walker Products link you posted, pdf page 17, Rochester 1-ME,1-MV. Part #1 is the solenoid, #2 is the solenoid spring and straight to the left is a threaded hole in the carb body.
Here is a picture I found, of one with an electric choke just above the solenoid. That is how
original solenoids were mounted.
[img]http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=523294&stc=1&d=1260657481[/img]
( Sorry picture won't load. Must be protected )
What is wrong with the carb you have?? Good question.
Everything you have read about adjusting the carb mixture screw needle, said to
lightly seat or turn the needle until it
lightly bottoms and then back out 1 1/2 turns or some number. The important word here is
lightly.
The carb body is very soft. If the needle is seated too many times, it can damage the seat. If the needle is seated too tightly, it can damage the seat. If the needle spring prevents you from feeling when the needle has bottomed out, you can damage the seat.
I fear "Mean Buzzen" is correct and that 1/4 turn is saying the seat is badly damaged.
I would do one thing before I bought a new carb. Spray "Carb & Choke Cleaner", all around the intake manifold and carb base to make absolute certain there are no more vacuum leaks.
I like carb cleaner much better than brake cleaner or starter fluid. It's not as messy, not as flammable, cheaper, and isn't as hard on paint.
