Will an engine harness interchange from a 78 to a 79 Dodge truck? Same size motors.

TIA.

I know the headlights and turn signals are different. If they are attached to the same harness (I no longer remember), than no, they won't easily interchange. Also 79 could have quad headlights.

79 was also some emission controls changes, so even if the engine only harness is separate, they still may not swap directly.

Well, at least it's a bump for you!

Pretty sure the lights are not on the engine harness.
I put a 78 into my 76 a few years ago.
Different direction, but I would guess it should be easy enough.
Emissions might have changed?

I think the engine one is the same as long as it's the same engine and emission setup because that went with the year and also how the truck was ordered.

Hugh I have done the opposite of your plans and mated a 78 bulk head to 79 engine and chassis harness there will be a few wire positions that will need to be changed if I remember correct I think it was three(I hade to mate entire harness though) Just take some time comparing wiring diagrams. the terminals come out easy when you push down on the small tab in middle looking in from receiving side of plug just give them a little push back up prior to inserting them back in proper terminal position, I got rid of all that diagnostic wiring too much cleaner looking