You don't want to fool around with a 1 ton they don't have the payload, the brakes are too small and the tires are usually not heavy enough.
I don't know what year range your looking at or a brandnew truck.
Myself I gave up on 1 ton trucks 10 or more years ago started with a 88 F-Superduty which is a F-450 in that year.
The 99-02 F-450s are not as heavy as the 03-09 F-450s. The F-550s from 99-04 have the Dana 135 the 05-09 F-550s are very similar to the F-450.
The 99-02 F-450 has a modified Dana 80 its not as strong as the Dana S110.
The 99-04 F-550 with the Dana 135 is a heavy axle it can take some weight it is a little heavier than the current S110 that is used in the F-550.
A 99-02 F-450 uses the same brakes as a 99-04 F-550 and 03-04 F-450.
Anyhow if your looking for a truck with a 7.3 then look at a F-550 if your not scared of the 6.0 a 05-07 F-450 F-550 is good.
Like I said there isn't much difference between a F-450-550 in the 05-09 year range. The rear suspension is slightly heavier in the F-550 unless you go with a 19,000lb gvw.
Most F-550 trucks have the 17,500 gvw.