Welcome to the forum Jim!
I like the LeSabre'* very comfortable smooth riding cars!
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Programming for a different tire size or rim can be done to adjust for speed errors for Obd2 cars.
The formula'* a little tricky in programming, but a knowledge tech at dealer should be able to accomplish input for new sizing.
If you were running the original stock tire size and the speedometer is out slightly, they would recommend that the speedometer be recalibrated.
Probably a tuner may know how to tune for 5 mph less based on an new input of a tire size though.