Honestly, if you want to do this swap go to the lt1swap site and do some reading there. You can also join the facebook group for LS swapped Squares -
https://www.facebook.com/groups/267895843406925/about/
Essentially you are going to need your motor, transmission, pcm, and wiring, if it is a dbw setup then you will need the pedal and the harness that goes to that and the bcm and tac setup. Likewise you will want to make sure you keep the o2 front o2 sensors, the driveshaft out of the donor truck, and while you are in there go ahead and pull the sending unit out of the gas tank and take the pump off it. If the radiator is in good shape in the donor keep it, along with the hoses, and take the MAF sensor and airbox/airtube off. You can also pull the coolant recovery bottle off, and if you keep all the hoses intact then you can swap that into your square as well. After that get you some Tejas Steelworks engine swap adapters, and you can drop the engine in and test fit. If you had a th350 or th400 in it originally you probably can use your transmission crossmember in the exact same location. After that either modify the oem exhaust manifolds or get you a set of swap headers (Hooker, Speed Engineering, and a few others make excellent sets ranging from inexpensive to quite pricey) and then you can just drop the front o2 sensors in them and hang them on your engine. After that its a matter of removing VATS and getting a base tune on the PCM, and having the driveshaft modified to fit your truck. Everything else, like the radiator and what not, should bolt in place of the original parts. You will probably need to make custom lines for the transmission cooler lines, run new EFI fuel line from the tank and then possibly a return line to the tank, replace your sending unit and fuel tank with a TBI tank (87 model C10) and put the fuel pump you scavenged on it. You can DIY your engine harness if you can read straight forward instructions and a wiring diagram. That will be about 300 to 500 bucks saved and most anyone on Swap forums has someone they can recommend to remove VATS and load a stock tune.... Once you get your fuel sorted, your cooling sorted, and reinstall all the front clip and have it running, then you can find a dyno tuner and get it properly tuned so your work will be long lasting.
You can essentially use everything that is attached to the engine, including the battery cables and grounding cables/straps.
There are cheap parts for eliminating the EGR circuit (highly recomended) and you can use the LS AC compressor on your older style AC system if you have AC. You just want to make sure and have the system bled down and sealed off until you are ready to hook it back up and get it pressurized again.
Hope that helped answer a few questions.
The LS swap is not terribly complicated but what you want to do is read a lot and do research to get a good set of reputable parts list before you spend your money and then be prepared to test fit everything once before making it final.
