94,
then I real dont know what that is. With a Lightning, the 8th digit in the VIN is a "R". With a VIN (vehicle Identification Number) the 8th digit descibes the Engine. The 10th digit tells the year.
I would say that the fact it lists it as a 5.0L confirms its not a Lightning. All 1st Gen Lightnings come with a 5.8L HO and automatic trans.
Check out EBAY, look up a Lightning and compare the VIN in those vehicles.
All will have the 8th digit as a R.
If you doubt the VIN plate compare with the info on the door plate.

The fact that it was a fleet truck tells me it may have been used as a TOW truck. I would look under the hood and see what the emissions tag says for year and Engine. If its a 5.0L its not a LIGHTNING.