On my 49 Dodge truck, I had to remove the factory motor driven fan because there wasn't enough clearance between the radiator and the water pump (you get that with putting a V8 and different chassis under old sheet metal).

My local Car Quest had a high CFM single 16" electric fan that has adjustable temp settings for the cooling speed settings. I bought the 16" fan because it fit the vary tight confines of the location it had to fit in and matched the height of my very small 4 core core Champion radiator. There is a temp range between the turn on and the turn off you can't adjust, but you can choose the high/low range of the operating temp. The fan comes in a kit with the fan, temp control thermostat, and a wiring kit. Its attached to the radiator with those radiator zip tie things and there are a few choices on how to mount the temp probe for the thermostat. This system has been on the truck for a couple of summers now and seems to be working well. You will need to make a shroud for it to work on your radiator, or there could be larger diameter fans (or a dual fan) system available. My point is, adjustable temp electric fan kits are out there. When mine kicks on, you can watch the temp drop on the temp gauge. It only runs a minute or two when the coolant temp hits your high temp range, and shuts off when it reaches the low temp setting. I have mine is wired through the ignition switch so it only runs when the motor runs, but it can be set up to come on ( and turns off) when ever the temp limits are hit.


With that said, making a very good fan shroud for your existing system may actually solve your cooling system problems. You really need to pull as much air through your radiator at idle speed as you can, and your current half azz shroud isn't doing the job. If the good shroud doesn't solve your issue, you can then simply buy the adjustable electric fan to replace your existing fan size.