Originally Posted by Irelands child
I have an extruded two pass, 24 inch long mounted on the frame rail of my '31. I also have a temp sender mounted in the pan and use a DPDT switch to the engine coolant gauge so I can monitor both with a quick flip of that switch - both run about 180 degrees F on a 90+ day. You can debate location of the sender, but the pan is the easiest for my application. Couple of photos attached:
That's just what I was talking about, switching senders on a single gauge. I think the pan works fine as a location for the sender. Thanks for posting how well that works for you. I know lots of guys who run an extruded cooler like yours, but very few that have a sender/gauge to monitor how it's really working.