My opinions: Keep in mind, I've been driving T-birds since 1993, all with OEM 16x7 wheels.
Stock 225/60's drive nice, look fine, but are a little too narrow for my taste. Lots of choices out there.
I had 255/50's for a while, Falken Ziex 512's. Looked great, especially lowered, but too wide for good handling. PITA to mount, and some shops won't even do them. The steering was too heavy and the car didn't feel like it tracked right. The selection in that size is pretty sparse, too.
I went back to 235/60's the last time I replaced them. They fit nice, no problems with lowered cars, and they track nicely like the 225's. Just a touch wider and taller than stock. I have Kumho Ecsta this time, reasonably inexpensive.
I've seen cars with 245/50's and they just look too small (height) to me. Same with the 235/55's.
97 LX, 4.6, Dynomax catback, Mustang MAF/intake tube and Aviator throttle body, Xcalibrator2 by Lonnie at BOC, 180 t-stat, Super Coupe wheels with 235/60/16's, Kenny Brown strut tower brace, Tokico Blues, Eibach Pro-kit, some strategically placed MN12 Performance polyurethane pieces, '02 Grand Marquis transmission
Submariners do it deeper...