I was wondering is there any way to tell by serial number or any other identifying marks on the engine if its a 4.0 or 4.6 litre. Thanks

 

My p-38 has 4.0 stamped on top of the intake and it also has it written on the tailgate. There should also be an emissions sticker under the hood which indicates the engine size.

 

I bet he is talking if it is just the block and not the whole engine. I am sure there is some identifier but I am not sure what it would be.

 

You could always measure the bore size, that is if you have access to the cylinders...

 

I was wondering because there was some question as to if the owner had indeed gotten a 4.6 when the engine was swapped out.
Since they look the same its quite possible that the owner paid for a 4.6 and got a 4.0 since the truck seems slow