69-70 K20 questions

[TwoFiftyShifter]

I have recently thought about trading trucks with my Dad. Both are project trucks that start stop and steer. I've got an 84 K10 and he has a 69 or 70 K20. It was previously a wrecker. I love the truck and it has less rust than my truck, but it just hasn't been down the road in 20 years so it will take some work. It has a V8 which might be a 350 and it has a 4 speed 465 tranny. I've driven it in the yard a bit, jeez it may have 4.57 gears. Base model as far as options go.

Which axles and transfer case would this truck have had if it was stock? What is the easiest way to get it to a 3.xx axle ratio for better drivability? I really like the 84 but it needs quite a bif of rust repair on the cab and the 70 is just cooler in a way. More potential? Don't have any good pics but here is one that shows the bed that had a wrecker unit.