I am wrapping up my gen 4 LS swap for my colly and just wanted to do a quick write up on here and share what I have learned.
Disclaimer: I am not a mechanic by trade and received a lot of help doing this project, I am not all knowing but I will try to answer questions to the best of my ability. I am also not a tuner but can answer some tuning questions as I talked with the tuner as he did the tuning and understand the process.
Ok to start, gen 4 is a pain in the butt. If you just want a running and driving truck I would recommend just doing a gen 3 swap even if its a newer colly(07+). The advantage of gen 4 is you can keep the gauge cluster functioning and functional ABS and traction control. I did this because I want a reliable daily and live in Chicago so ABS and traction control really help in traffic and winter. So if your build is for power just gen 3 it, many more people have gone that way and have found good work arounds to major issues, as well as the tuning being more straight forward and supported by more tuners.
The major things I had to do:
Gen 4 has AFM and VVT, had to remove those because of the problems they cause for higher mileage vehicles.
New exhaust manifold and exhaust system because Silverado one will not fit.
Custom wiring harness from CPW (I'll go into detail on them later)
Different oil pan - my colly is 4wd and stock wont fit, 2wd swaps might not need a new oil pan idk though
New rad fans - mine are from 98 intrepid but I know a lot of different vehicles rad fans will work
Trans was a 4l70e not a 4l60e, I have not heard anyone else talk about this but if you take it to a shop and have them rebuild it as a 4l60e it will not work out and if you are me-you will blow your trans up and be down another 1.5k and stranded on the side of the road.
I will update on trans when I wrench on it some more.
Custom motor mounts - I ordered custom ones from CPW but needed to be shaved down a little bit more on the tops of them to fit perfectly, custom ones can be made too, I just wanted to save time
I ordered this
kit from Glensauto Performance. TSP was in backorder for cams but this company had them in stock. My donor 5.3 had 180000 miles so I knew I had to rebuild and this kit included everything I needed. The only thing is that it comes with the wrong cam position sensor that has to have the wires (2 and 3 I believe, will double check soon) switched to run(or just keep the old position sensor).
Random stuff: Trans cooling lines and fuel lines will have to be changed, the alternator on I5 on V8 are not the same unfortunately, you can also save money by ordering an air intake for Silverado/Avalanche instead of for a Colorado LS and just modify it to fit as you want and finally the I5 fuse box will work for the V8. In addition the MAF sensor has to be facing upwards and for the most part closer to the throttle body then the air intake or else you will get a code.
Now to talk about Current Performance Wiring. As of now they are the only place I could find that could make a plug n play harness for this swap. They are a bit of a pain to deal with though. They never answered calls and usually took a couple days to respond if at all. They do respond to emails in 2ish business days so just email them. It also took over six months to make the harness. I understand this is because they are busy and backordered but originally told me it would take just 6-8 weeks, then that timeline was extended every time I talked with them. Either way, harness did fit and took only a couple of small modifications. The only things are the starter wire doesn't work so I had to take an S10 starter wire from my buddies old project to get it to work. Also the plugs to the O2 sensors are male when upstream O2 sensors on the colly and Silverado are also male. The work around is to buy downstream sensors for the silverado and make a small cut in the plastic to fit them together, it will still read and work perfectly. Besides those small issues I am very happy with the harness. It is conveniently labeled and is the proper length everywhere. The whole gauge cluster works along with ABS, TC, the transfer case and after the ECU was reflashed the fans will even kick on at whatever temperature you want (I5 is belt driven fans).
As for tuning I know I guy who does mobile tuning for LS's. The problem for gen 4 is no shops at least in the Midwest do bench tuning for e38 ecu's. You will have to either tow it to a shop or find someone to come to your garage/shop. The tune is just a Colorado LS code segment swapped to ECU and TCM. If you do AFM/VVT delete that will have to be programmed in as well.
Final notes, all this info is assuming some experience on LS platforms, if you want to learn more on the rebuild, cam swap and that stuff there's a load of info on YouTube and forums. I know this post is not super detailed or organized I just wanted to get it all online and will revise it when I have more free time. Feel free to comment questions or let me know what you think on the project and I will try to respond as soon as I can.
link for oil pan - Chevrolet Performance 19212593 Chevrolet Performance Musclecar Oil Pan Kits | Summit Racing
link for exhaust manifold - Patriot Exhaust H8097 Patriot LS Cast Tubular Manifolds | Summit Racing
The exhaust manifold will say it does not fit on gen 4 5.3 - it tucks really nicely and to my knowledge LS's are universal when it comes to exhaust manifolds
If you are going to copy any of this information please just give me, Nate moyds4, credit, thanks.