700 R4 swap 72 K10

[Nitis]

I have a 72 K10 that I am trying to decide what direction to go with I am a firm believer in overdrives and am still seriously considering an LS swap which would constitute no need for this conversation

But I think I could more easily justify building a new engine now pairing it with the current turbo 350 then later add the overdrive tranny

So what mods could one expect going from TH350 to 700r4? Will I need new drive lines cut or lengthened? What else will I have to do?

Sorry not a mechanic just trying to get an idea I know overdrive will help make the truck more driveable and squeeze some mpg out of it too