Old post, but for anyone interested the GM part number for this switch is 14080627.
Yeah, I got one of these M4MED on my donor engine, dual capacity pump
I Found the following after much searching on the web:
What I need is that outfit that is screwed into the thermostat housing that provides a ground and completes the 12 volt circuit to the idle mixture solenoid on the carb of my 1986 pickup with a 305. My local Chevy dealership called it an "accelerator pump coolant temperature switch" part# 14080627, and said it was a discontinued part no longer available.
http://www.trademotion.com/partlocator/index.cfm?action=searchCatalogOEM&siteid=214727
Go here, enter the part number. it came up as available when i did it, $65.00 or something like thatend quote
It is almost $67 for the switch as of this post date.
don't know if it is new.
When I install this carb on my 383, I think I might add a toggle switch and do a manual switch: See what happens between on/off
dougbert
Below is picture I found from the internet of one in the water neck, circled in purple.
The circled in red is the connector to the selenoid.
Cannot find the connector, nor the switch, save for above. Only made for 2 years, 85 and 86