I used Old Air on my 261 and the biggest issues were the compressor brackets, pulleys and under dash unit. All in all the install was easy.
You are in a fortunate position in the sense that you have a 292 in your truck. GM put A/C in lots of cars that came with 292s, including camaros and trucks. So, you can probably find the bracket, compressor and underdash heat/ac unit from a vehicle with a 292 and put those parts into your truck. I'd get the guts and controls from the junk yard, including the compressor, bracket, harmonic balancer/crank pulley, dryer, evaporator, condensor, expansion valve and a/c lines.
You should replace the dryer, convert the compressor to 134A and get your controls and vents aftermarket. The main components for factory air are good quality stuff and available over the counter when it comes time to service them.
My personal favorite is the underdash faring with vents and the controls that are hidden in the speaker grill. However, what I've got is the underdash faring with the controls in it and I'm in the process of painting the fairing the color of the dash and putting stock knobs on the controlls so they look less out of place.
It may be a pain in the rear to pull the parts but you'll save money in the long run and I think the factory a/c is pretty solid stuff.
