Fan On-Off Temperature Settings for 180 Degree Thermostat

I have a 1989 Ford Mustang with an upgraded larger aluminum radiator, twin Ford Contour electric fans and a 180 Degree F thermostat. In the tune what would be the right fan on/off temperature settings I should use based on my setup? I have on order fan controllers for an 07 Ford Fusion PWM type controller however while I wait for those I would at least like to know what ballpark I should be setting the fans to.

I would turn the fan on at 185 - 190f, and off at 180. If you have the ability to lock it out when moving, usually 40 mph is a good target for that.

As David said, a 10 degree difference will prevent the fans kicking on and off too often. Assuming you've a pressurised cooling system and/or some form of additive that affects the boiling point, I'd look at 10-15f above the nominal thermostat value, though, as that's usually the range between starting to open and fully open - you can check this with a thermometer and suspending it in water being brought to the boil, to check, if desired.

Something that is often overlooked, or not thought out, is the shroud design and fit. Make sure you set the fans back from the matrix so they draw through more of the area than right in front of them.

If you have a large area around and/or between the fans, you can buy factory style "flapper valves*" that, when fitted properly, allow air to pass through the "blocked" part of the shroud as well as the fan openings, but when the fan(s) operate they're pulled against the shroud, sealing them and forcing the fan(s) to draw all the air through the matrix.

*Like these - https://www.demon-tweeks.com/nz/spal-fan-shroud-rubber-flap-spl3013-0012/?srsltid=AfmBOorUo9VG9LpDeGAuzPKe1JDUkjfNpxJTECbwBm9s6DBc7iGgsDjO

There are many examples, and types, or you could make your own up from some thin neoprene, or rubber, sheet.

I'll just add that where the temperature is monitored is a significant factor in this. You generally want to sync up with the thermostat behavior, but temperature at the thermostat housing and where your temperature reading for your controller are taken may be rather different.