i have an 03 GMC 2500 HD 4x4 with the 6.0L in it right now and its comin around to its last leg. so i was thinking about putting a duramax in it and was wondering what all is needed to do this such as the right engine model, transmission, transfer case(if needed for the swap), etc. i knew this would be the best place to ask so any help would be welcome. i also heard that the wire harness is the same and all i needed was to swap the computer and the gauge cluster, is this true?

I would talk to dmaxallitech for all that info as he can pin it down for you.

I would venture to say that changing the fuel tank and lines would be in order as well as the other items you listed.

Find a wrecked donor and swap the drivetrain and other parts over. Since you have an 03, you can run any Dmax version, 2003-2007. A 2006-2007 LBZ drivetrain with the 6 speed would be ideal, but costly.

Id contact duratothemax, TDIguy, boisebiker or theferminator, as they've all done similar swaps and would know the pratfalls and problems.

Find the thread titled Yukon Duramax and this will answer a lot of questions that you don't even have yet. As for the engine you can use any duramax from 03-06 I know and possibly 07-08. Do you use 01-02. You will need the matching Allison and transfer case. There are 5 speed and 6 speed Allisons and they are not interchangable and the transfer case is specific to the Allison transmission. Best thing you can do is get a donor truck.

Sound like a mojor project!!

For starters
lb7 engine
Allison auto or zf6 manual
wire harness
PCM
tcm if you want an allison
cluster
hydroboost
probably new engine mounts
t case
new drive shafts probably
I'm sure there's more you'll need

boise's thread:
http://www.dieselplace.com/forum/showthread.php?t=148819&highlight=Yukon+duramax

thanks for all the help. that thread did help alot. but does anyone know where i can get a donor truck?

IDK where you're located but there is one in waynesboro,tn. Not sure what year but it is on the nashville craigslist for 6900$. Think it might be a little cheaper for just the engine, trans, and drivetrain but not sure. The place has a lot of old dmax's. Here's a link to one http://48creekautobrokers.tripod.com/ Hope you find one and good luck!
Here's a link to the page its on. and its 8900 my bad http://48creekautobrokers.tripod.com/page09.htm

I know of one in Idaho, totaled because of a cab fire. Rebuilt tranny, new transfer case, EFILive tuned ECM. Was available 2 days ago. PM me for details. If I was closer and ready for another conversion this would be the one I buy.

thanks for all the help. that thread did help alot. but does anyone know where i can get a donor truck?

If you are near Colorado type Klode auction denver into your search engine. They auction insurance totaled vehicles. Down side is that you have to go to the auction so distance is a factor.