5.3/4L60E Harness Question????

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I am wanting to put a 5.3 in a 64 C-10. I am wanting to do a 4L60E or 4L80E for a transmission. What exactly needs to happen for the transmission harness? Do I need an internal or external or both tranny harnesses? Do they need to be modified?

I do not have the 5.3 motor yet. The one I am getting is from a JY 100% complete (accessories, harness, ECM,etc.), BUT I am sure it will not have the transmission harness (at least I dont think it will). I am doing some swapping for a stock 4L60E/4L80E Trans. I am not sure if it will have all the wiring it needs either.

This my first attempt at late model electronics (350/400 bolted to a 700r4 is my knowledge) and I am very neverous trying late model electronics. I know its better and time to move out of the stone age.

I am trying to get everything sorted out before I start buying anything.
I am sorry if I seem very novice in my questions, I am just trying to get all my eggs into a basket. Any response would be greatly appreciated.