Stock replacement, all AC Delco, you can go to their website and look up the part numbers online, and a good Advance Auto Parts will be able to order what they do not have.
You can go MSD for everything ignition except the spark plugs, and see a very slight increase in fuel economy. It'll take a long time to pay for it in savings though.
Set the timing to 8-10 degrees advanced.
Switch to a good quality 10W30 synthetic oil (use a K&N or Wix filter).
I get longer life and a little better performance/economy from the AC Delco Rapidfire plugs.
Don't forget the fuel filter, and the PCV valve.
If it has not been replaced recently, a new AC Delco oxygen sensor will probably help.
Free flowing exhaust will help fuel economy, if you don't use the extra power and enjoy the better sound.
Switching rear end gears will require changing the speed sensor buffer to correct the speedometer, and prevent possibly setting codes in the computer. You have to switch both differentials out to match with a 4x4, or you'll kill the transfer case. It's a lot of work on the front of that truck.
Synthetic gear oil in the differentials will help (in the transmission, too, if it is a stick shift).
A proper alignment will help. As well as the previously mentioned proper inflation.
It's the little things that add up.
