SHELBY GT 350 Member
Joined: Sep 2010
Location: see user name
Going purely by the evidence that one wheel is warmer to the touch than the other definitely suggests a sticking caliper. I would start by removing the affected wheel and inspect the brake pads. Even wear between inboard and outboard is what you're looking for here.
If uneven wear (but pads are still good), I would remove, inspect, clean and regrease the caliper pins. Put it back together and see how things go. If you need to or want to replace pads then go for it. On that note, I would probably visit all 4 corners and clean/lube the pins.
You have a car that has spent most of its life sitting. I'm sure you've been here long enough to notice the abundance of sticking/hanging caliper threads every spring when the winter crowd brings their cars out of hibernation, it's a fairly common issue with cars that have been subjected to long term storage or infrequent driving.
The problem could also be the caliper itself, but since the above is cheaper and easier then that's where I suggest you start.
2001 GT Convertible
All the usual bolt-on's /200 I6, C4
And a few Explorers too... 2008 4.0 XLT 4x2, 1996 XLT 5.0 4x2, 2003 Sport Trac XLT 4.0 4x4