I've got an 04 with a bad eng. Will a 4.7 from a later model work? I have a complete wrecked 5.7 hemi truck, what are he pros and cons?

 

One of the biggest problems you will have from changing out to a later model engine is that the wiring harnesses were changed mid year in some of these vehicles. He two that they have are JTEC and NGC. If you purchase an engine that has the opposite wiring setup your going to end up spending thousands of dollars getting it to operate correctly because of the electronic and mechanical differences. So first off I would check your motor to see which wiring system your motor is running on. After that its just a matter of finding a similar wiring set up on a later model.

As far as the 5.7 Hemi goes, I have never done such a swap. But the problems I could see you running into would be the fact that a Hemi motor would leave you less room to work on if something broke. The cylinders would be facing directly towards the fender wells, so if something broke internally you would have to pull the whole motor to work on it. Also figuring out if the power steering pump, alternator and all other components would fit without bumping into the radiator or body panels. Plus the fact that you would also have to redo the entire wiring harness to accommodate a 5.7.

If you don’t mind me asking, what happened to the 4.7 currently in the truck, and are there any modifications that you made to the engine?

 

Bone stock other than spectre cold air intake, 119 k miles, haven't taken anything loose yet but I have the hemi ready to pull from other truck. Like the idea of hemi other than mpg, but nervous about 4.7 (time bomb?)

 

Ya I can understand being nervous about the 4.7 time bomb, but to the same effect there are issues with the Hemi as well, dropping valves and blowing the motor at 60 to 70 thousand miles is a pretty usual occurrence lately. I don’t know how many miles are on the motor that you currently have sitting, but you may want to do some work to it before you put it into the vehicle.
Also I don’t know what your budget is or how much time you have to put into it, or whether you want to take it to a shop to have it done.

Whichever way you decide to go I would recommend doing some work to any used motor before you install it into the truck. Check compression, so on and so forth to make sure the motor wont fail you soon after installing.
What city are you in? I'll see if my local custom shop has a wiring harness for a 5.7.

 

Do a search the 4.7 to hemi swap has been done more than a few times and is fairly well documented.