I've not tire shopped for my Mooney in several years, but the best I can remember the main difference between Flight Custom 1, 2 & 3 is the speed rating and the price. FC3 cost almost double FC1, and have a speed rating of either 140 mph or 140 knots. For my plane, Vgo = 120 mph, but the tires will never touch the ground at that speed. My preference is to land with the stall horn squalling, which is generally in the low-60-mph range. Why pay more for stiffer sidewalls and higher speed ratings? Oh, yeah--takeoff, right? My Owners Manual says to rotate at 65-75 mph.
So the much less expensive FC1 works just fine! At 2575 lb gross weight, that's not a factor, either. Besides, when you price the tubes, you'll be glad to buy the less expensive tire . . . . .