well if it's a short 1/2T, then the tag or cab's been changed - does it match what's on the title? a 3100 VIN would start '3A' [3= 3000 series, A= 114" W.B., only made in 1/2T] - 156 should be a trim code
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics
