Sanden compressor

[Charger jUNkiE]

I put a sanden compressor in my retromod project. The guy that did my A/C fittings said I should probably get a thermostatic switch to let the compressor clutch cycle off and on otherwise it could freeze up the evaporator and the plenum.  My question is what is considered the "upper Plenum of a stock 1970 B body AC box and where have others mounted their switch and where did you tie into the clutch power line, wiring.