Adjustable electric fan thermostat question ?

You can always wire in a switch override.

Best of both worlds

35 years ago i had an electric fan on my 63 econoline with a 289 v8 swap. The controler had a bulb and tube like the one in photo 1. It also came with a rubber shim with a slot in it. You put the rubber shim on the upper rad inlet tube then put the bulb tube in the slot then slid the hose on over it all, then hose clamp. No leakage

You could always do like the modern cars, and have a lug added to your rad and put a thermostat switch in it