billy, im new to these trucks, but the transmision is specific to the td, for sure.i beleive the radiator is also,but things like suspension etc. should be the same... as for a swap to a gasser body, i would want them side by side, and meticulously cross referance as you go..definatley the fuel line/return seemingly would be important as well as i think gassers have pumps in the tank?? wiring harness it seems would be important for glow relay, and i may have overheard something about the tach...
hopefully some more experianced soul can verify/correct and or ad too this for you. fox