This is the fan system I have on my '71 C/10.. No computerized engine management system. Just a rambunctious carbureted 454 BBC. One fan comes on with a signal from the ignition switch.. The other fan is activated by a coolant temp sensor, set to come on at 195 Fahrenheit.. The second fan very seldom comes on. I live in East Texas where summer time temperatures run consistent triple digits.. They're not cheap, not very pretty, but they WORK!!!
https://www.summitracing.com/parts/der-16826