Well if you crack open a 1977/1978 Dodge truck FSM and check out pages 9-49 9-69 you will see that they were producing both 413 and 361 engines. Pages 9-95 9-96 list the specs. Two flavours for each size.

My father had a 77 D800 with an Industrial 413. The nieghbour down the road had a 76 D600 with a 361.