JBert and Old Goat Ninja thanks for the info. I currently have 235/50/18ís.
So you will need new wheels to go with those tires; and they should be at least 9.5" or better yet 10" wide. I don't know what price you found on the tires, but I'd suggest you look at the total cost for the wheels, tires, and TPMS sensors.
Regarding the tires, here is info I found for you on Tire Rack:
235/50R18 example (you'll get better information if you look up your exact tires, but this should be fairly close) https://www.tirerack.com/tires/tires...omCompare1=yes
diameter = 27.3", which is typical of the "normal standard factory tires" on these cars
275/40R20 example (same make/model as above for comparison; again you should look up the exact tires you are considering, but this will be very close) https://www.tirerack.com/tires/tires...omCompare1=yes
diameter = 28.7" ; which is just about 1-1/2" taller than the originals, like we guessed earlier
measuring rim width is 9.5" ; rim width range 9-11" . . . you really want your wheels to be the measuring width or wider
If your car is not lowered, I think they will probably clear, but not sure. A while back I learned that Ford still engineers these cars with enough clearance for tire chains, and I assume that is still the case . . . but I really don't know for sure if those tires, which are both tall and wide, will clear.
Also the speedometer will be off a bit if not recallibrated -- you will be going a bit faster than the speedometer says