1999 F 350 Dually 4 door motors

I am trying to research to find info about the types of motors Ford installed in the 1999 F 350 4 door Dually pickup ?
A person from church is selling one with this title and I want to know if it is a diesel or Gas motor without needing to wait to call him : )

5.4 v8 gas
6.8 v10 gas
7.3 v8 diesel…8th digit of vin is an F

Have you see the truck ?
The label on the fender will say enough to learn gas or diesel.

For a 4 door dually, you really want the diesel. The gas engines , even the V10 in the early Super Duties were a bit underpowered. If you want a gas engine, try to get a 2005+ model. The 3 valve 5.4L and the 3 valve V10 were much more potent and somewhat more efficent than the older 2 valve models. The 5 speed torqueshift transmission was also a big improvment over the old 4 speed units in the older trucks.

However if you want a diesel, the the 7.3L is a better choice than the later 6.0 and 6.4L diesels.