Matt,
First thing to do is jack up your truck, remove both rear wheels and put two lug nuts on each wheel and snug them down. Now measure from the outside of the drum to the other side outside of the drum, this is the measurement that you need. That is the width of the rear end that you need to find.
Now, do you want 5 lug or 6 lug? If you are going to go with disk brakes on the front, car and some truck rotors are 5 lug, so you will want a 5 lug rear end, so you don't need to have two spare tires. Some trucks have 6 lugs on the rotors and rear axles. What is important is that you match them so you don't have two spares.
The steering column is a different animal all together. The factory one is one piece from top to bottom. A newer column will be two pieces, a steering box and a steering column. Can you change them? Yes you can , but you will need to get an aftermarket kit to do it properly .
Hope that clearly answers your questions.
