I can't speak to FE's, but I have done this exercise on smaller engines (single, V-Twin, and Inline Twin two and four strokes) in the past. I would drill and tap dozens of holes into the water jackets around the cylinder and throughout the heads and install thermocouples. It wasn't unusual to have 12 to 16 thermocouples mounted in the cylinder, and another 8 to 12 in the head on these engines. This was almost always done on prototype engines, or new designs to make sure there wasn't any problems during initial run-in and fuel mapping. Generally speaking, there wouldn't be more than a few degrees difference between the thermocouples, once the engine was up to temp. Warm up would show a bit of difference, especially with the thermostat closed.
The one engine that would show a large temperature difference would be the direct injected two strokes. The fuel was sprayed through a window in the piston towards the transfer ports. The spray pattern would hit the opposite side and keep that cylinder wall considerably cooler. Took a looonnnng time to figure out how to properly cool the piston on that design to keep it from splitting along the window and sticking in the bore.