Hey all, first post here and it may not actually be in the right spot so sorry if not. I just bought a 5.3l from a 99 silverado with the wiring harness and ecu to swap into my 79 Malibu. I plan to use a 700R4 as my transmission. I keep hearing different things so wanted to ask on here. What do I need to make the transmission and engine mate up properly and work correctly? The engine has the stock flex plate which I hear will work fine if I elongate the holes with the stock torque converter from the transmission I use. Is that correct? I also hear that I need to run some sort of spacer and longer bolts in the flex plate? I found GM part numbers somewhere but lost them so if that's right and someone know's please let me know them again. Also can I just use the stock engine harness and ECU as is? I know that I'll have to run some wires inside and such but not sure. First swap of this kind and not new to performance but new to V8 swaps. Also my car is that factory V6 and I know that g-body V8 mounts will work with the "swap mounts" out there but does anyone know if the V6 mounts are the same? I basically want to get this in as quickly as possible for as cheap as possible and running correctly. After I get it in and running I will start removing the things that I don't need and connecting the things I do need/want like ac and power steering. After that is done I'll slowly start to upgrade the performance. Any tips or advice is greatly appreciated unless it's negative. Thanks in advance!

 

You should visit lt1swap.com, there is a wealth of information there. I know it's possible to use a 700r4 on an ls but it may end up costing as much as getting a rebuilt 4l60e. With a cable throttle body you have to have a bracket for the TV cable that the 700r4 requires, you can program the PCM for a manual trans so it doesn't have to communicate with the 700r4, but the PCM still needs a speed signal to work right. Some have made their own, or use a conversion box that turns the 700r4 mechanical signal to an electronic one the PCM can read but I think it's pretty pricey.
You use the pin outs on lt1swap to make the stock harness standalone, the sites owner can even flash your PCM to remove vats and emissions and whatever else you might need to get the vehicle running. The wiring isn't too difficult, you get Rpm, and speed from the PCM. Oil pressure, water temp, fuel, battery you get from the vehicle or use adapters to put your old sending units on the new engine.
I recommend using an adjustable motor mount bracket like dirty dingo's to make installation easier, and you can slide the engine to exactly where you need it so you don't have to change your drive shaft.
You should install the engine with the power steering pump, take your old high pressure side hose and the new pump to a hydraulic hose company and have them make a hose that fits the new pump and old steering box.
Putting a Zo6 cam and springs is a relatively cheap performance upgrade that is much easier with the engine out, most people replace lifters and oil pumps at the same time since those are also relatively cheap to replace and will increase your engines reliability. Then once you get the car driving you can get it tuned either on the street or on a dyno.

 

Welcome to the site, there's a wealth of great information here and I'd suggest that you take the time to read, re-read and then....re-read the info, take written notes and be patient. With that being said, the fact that you're building a car that had an entire thread devoted to it can only help. Please read and search the g-body swap thread, and then read Mervs thread as well. You can use the search function within the threads to look for specific info, as stated above Lt1 swap has a wealth of wiring info. Personally I've read and compiled info for years with most everything needed before I attempted my first swap. Good luck, and ask away after reading, for confirmation.