Transmission option for LSx swap

[Mikes71Chevy]

Hello everyone,

I have a 1971 C20 with 350/350 combo that I will be swapping out for an LS engine. I've recently purchased a 5.3 L59 engine with DBW out of a 2004 GMC Yukon 4x2. It is a complete engine pull with wiring harness, ECM, gas pedal, etc., but no transmission.

I need a transmission. I know a 4L60E is mated to this engine originally. After looking through craigslist and ebay, I'm overwhelmed by the various types of vehicle this tranny goes into. I have some questions below.

Should I look for a 4L60E around the same year as my donor vehicle or will newer units from similar truck work, also?

Is a used 4L60E with less than <75K miles still serviceable or should I look at a rebuilt one?

Does a rebuilt 4L60E come with electronics or do I have to buy them separately?

I know I can use a 700R4 with this engine. Is there a pro or con with using this transmission? I am leaning towards the 700R4 partly due to no electronics involved, thus less things to break. But if the con out weights the pro, then the 4L60E it will be.

I'm also unsure if the wiring harness from the engine has the TCM (transmission control module?) with it. The engine is on its way to my house right now. I should get it by this Friday. Not in a hurry to buy the tranny, yet. I'm still in information gathering mode.

This is my first restore/mod project truck that will be used for towing a small bass boat on occasion. I will post pictures once I've gathered all the parts for my build.