'04 LS V6 to V8 conversion?

First, let me give some back ground info. I have a 2004 LS V6 that was bought used in June 2006 with 29,000 miles. It's currently at 170,000 miles. The engine was replaced with one from a wrecked car in the spring of 2007 at 63,000 miles due to a screw up at an oil change joint, and it's still running, sort of... Despite that I just did plugs and new coil packs recently, it still has a bad miss-fire on really cold mornings and it's in general getting terrible gas mileage, but at least the constant miss-fire it had is gone.

The transmission started going screwy at about 125k and continues to do so at 170k. Holds out shifts and then jerks violently when it does shift, sometimes it refuses to shift and you have to put it in D4 and put the pedal to the floor to get it to straighten up. Sometimes the car starts miss-firing in a manner that almost sounds like it's doing it on purpose, looses all power and won't go faster then 20 mph. A little wrench light flashes on the gauges when it does this. Have to shut the car off and start it back up, then it runs normal again.

As for the body of the car, the suspension is still tight and rides great. The steering has play in it though, however I can't find anything loose or worn in the suspension, so I assume it's a problem with the steering rack itself. It also has a bit of body damage where someone backed into the drivers side door.

So to the point... I found a guy locally that is selling a totaled out 2003 LS V8 for very cheap. The engine and trans are in great condition and relatively low mileage.. Has good doors, some interior pieces I need that are worn in my car, etc. So I'm thinking about picking it up and swapping the engine, trans and everything over to my '04 V6. I am very mechanically inclined and have no doubt about my aptitude when it comes to physically being able to swap the drive train as I have done engine swaps in several older cars and trucks, however I'm just wonder what I'm getting myself into as far as interchangeability goes? Will it be pretty much plug and play, or what? Keep in mind I'd have the complete donor car available to take what ever I need.

Thanks.

You would have to swap most of the electronics, and some of the wiring harnesses. The electronics swap probably wouldn't be too hard, but the wiring harnesses will likely be a very big pain. If you want it to handle correctly, you will have to do some suspension changes too. Also, there are little things to look out for too. For example, the V6 doesn't have an aux coolant pump, but the V8 does. You would have to transfer the extra pump and plumbing over too.
If you are doing this as a hobby, then have at it. If you are trying to get a V8 LS at the least cost, then sell your V6 and buy a working V8.

Poor deliverability of an Engine will give false symptoms ''shutter'' to a good transmission, a V6 is cheaper to fix than V8.I have heard of a shop replacing a Transmission, Engine, and a new throttle body @ the problem. $15k Root problem was a stickey throttle plate on the electronic throttle body.