Time to prepare the engine for installation...
If you don't have a wiring harness, time to order one now. There are many suppliers of engine wiring harnesses. From looking around all over the internet I have to agree that the
Nelson Performance - Performance without Sacrificing Drivabilityharness is the best value around. When you order your harness be sure to know where you want to locate your PCM. The factory PCM is located behind the glove box. A good place to locate the PCM is on the passenger fender well. Take a measurement from the center of the firewall and then follow the routing you want to run the wires all the way to the PCM location. Give John and Allen that measurement so that they can make the wires long enough for your needs. Let them know if you have removed any smog devices and they can delete them from your new harness. They will need to know if you have a cable or electronic throttle body.
If you have a stock factory wiring harness that you want to try to convert, you will have to work out the wiring. Pink wires are typically switched 12V supply, red wires are 12v constant, dark blue and dark green control the electric fans. The fan leads provide a ground for relays. Below is a post I did years ago on LS1Tech.com and someone quoted my post in their conversion topic. There is a lot of good information there.
LS1Tech conversions
Bolt your engine adapter mounts to the block with the triangular portion towards the front of the engine using the supplied hardware. Do not put a bolt in the bottom forward hole, that hole will be used to mount the engine mount receiver cup. You may need some of the stock engine mount bolts to complete the installation. Some adapter plates use metric bolts and others use SAE bolts so be sure you have the correct thread pitch, don't cross-thread them by accident. If they get hard to turn try a different style bolt. Metric bolts have a number such as 10.8 on the top and SAE will have lines, 3 or 6 typically. Time to bolt on the engine mount/receiver "cups". The cups should have three holes to bolt them to the adapter plates. The bottom one will use a metric bolt, the two top ones you will have to check to make sure if they are metric or SAE. One thing I do to help the cups sit best on the adapters is to either to flatten or remove the raised section that mates to the adapter plates. If I don't have a torch to heat the detent area I take a hole saw close to the same size and drill it out and then grind off the rest of the raised section. If you don't do this the distance between the engine mount cup holes will be much greater than the distance between the frame mounts. You can verify this by measuring the distance between the mount holes on the frame and then using two plumb bobs or weighted strings hanging down from the mount holes on the engine. Most times I still find myself having the coax the mounts a bit during the install. Some people will slot the holes on the crossmember to allow a little adjustability of the mounts. You'll need to slot the holes about 1/2" on all six holes to do this. You'll also want to take off or leave off(if you converted from a V6) the lower control arms until the engine is installed so you can tighten the rubber isolator mount bolts after the engine is installed. Be sure to have all six nuts and bolt installed loosely before dropping the engine in if you're going to attempt this method.
Remove any exhaust parts beyond the manifolds, any pipes or convertors that may have come with your take-out assembly.
If you are going to reuse the transmission cooler lines from the LS1, leave them on because they are tough to install later, just watch that you don't crush them on the mounts when installing the engine.
Remove all radiator and heater hoses remnants from the original vehicle. It's much easier to do it now.
DO NOT install your new oil filter yet. If you bump it into something and dent it in the least bit while installing the engine you have to pull it off and throw it away. Want to know how I know? A dented filter cost me a rotating assembly when debris bypassed the filter because it was dented and oil was able to flow around the filter rather than through it.
When you have the engine installed, a common issue is the alignment of the holes in the mounts to the engine mounting cups that are bolted to the block/adapters. The holes are usually off by about 1/4". What I do is get one bolt in on the driver side and then put my hoist chain to a bolt hole on the driver side and lift just a bit to put a load on the rubber mount. That will give you the alignment for the passenger side hole. Just play around with it for a little bit and all will line up fine.