How do I tell what exact engine I have to match for a rebuilt one?

 

The easy way is to read the engine ID number off of the left front corner of the block, if a V-6 or V-8, or on the side of the block if a V-10. For example, if the characters starting at the third position are "5.9L T", it's a 5.9 liter truck engine.

You might want to snag a factory service manual for your model year from the FAQ/DIY section of the forum.

 

Look at the 8th digit of the vin.

C = diesel
W = V10
X = 3.9
Y = 5.2
Z = 5.9
5 = 5.9 HD

 

And hope no Dodge Forum member has been at it and swapped in a different engine!

 

Possible but unlikely. To be sure look on the side of the block.