I just went to the Ultra website and it shows it doesn't work on F250-350 6.0 trucks.
Find the /Vehicle Gauge Availability Estimator\
This utility is by no means comprehensive and is a work in progress, and your vehicle may or may not be listed. If your vehicle is not listed, it does not mean that your vehicle is not supported. It only means that currently this utility has no information about your specific vehicle.
Until they say that the 6.0L is supported, I wouldn't buy it.