Any help finding a vacuum switch from an 81-83'ish model??

[shiner2001]

I normally post over in the 67-72 forum, but have a question for you guys here. In my 64 El Camino, I have a 700r4 that I just had rebuilt and beefed up. This car is heavily cammed and according to my mechanic that did the trans rebuild, the heavy cam and torque converter aren't playing too well together. He says this can be fixed by adding a vacuum switch from what he said was about an 81-83 model Chevy truck. According to him, it's located under the hood on the firewall, just to the left of the steering shaft and brake booster (where you'll find a wiper motor on lots of vehicles from what I gather). He says this switch will have a vacuum line from the manifold on one side and a two wire connection on the other. Can anyone here shed some light on where I might be able to track this switch down? Mechanic says it will be a junkyard find, but I'd sure like to find a new one if possible. And if anyone can give me specifics on the part number/name/years/applications of the switch, that would be a big help if I need to head to the the pick-n-pull.

Thanks in advance guys, I appreciate it!!