difference between 01 and 03

both are 2.7,manual,4x4,extended cab, specifically wanting to know more about harnesses and connectors,etc....

 

Drive-by-wire

That and 2 years

 

Don't know for sure all I can say is be careful when swapping wiring harnesses between trucks, manufacturers sometimes make seemingly insignificant changes in wiring that can cause alot of headaches when swapping wiring harnesses between 2 vehicles that are otherwise the same.
It's always best to verify part numbers on wiring harnesses to make sure they are the same before attempting a swap.
Also alot of early model vehicles were either California emissions or Federal emissions and there were differences between the 2 as far as engine electronics go.

The 2.4l and 2.7L didn't get drive by wire on 1st gen Tacoma's, only the 3.4L did.

 

This.