Considering the Gen III 5.3 puts out at most 305HP and 335lb/ft a stock 4.0L puts out 210HP and 254lb/ft. A GMT800 silverado is anywhere from 4000-4400lbs
(curb weight) while a 98-11 Ranger is 3000-3200lbs
(curb weight) that gives .07 HP/lb vs .07 HP/lb factor in most 1500's run 3.23-3.73's while most Rangers are packing 3.73 and 4.10's no wonder you are out running the silverado's. On top of that the 5R55 vs the 4L60...add in minor performance mods on either truck and the Ranger still has weight on its side.