Where to get a 75amp relay for e-fan

Yes you need a 75a relay. I forget where I bought mine, it was years ago when I got it. Try doing a search for bosch 75a relays online and see if you can find places that sell them.
 
I forgot the link or the name but I was recomended to buy this controler from someone on here, it works very good, and since then I have never had a problem.

If you do buy a relay, I think GM has a thermostat that will send a signal to your realy so you wont have to use a switch
 
If you do a search for Baskin, he is the owner of DCC, you will find how to order. You have to send him a email and see if he will allow you to order.