In my opinion diesel trucks are the way to go.

There are many aftermarket things that you can do to a diesel truck. These depend on what type of truck it is and which motor it has. Big power, big lift, big tires, pretty much big everything.
There are three main types of trucks that are American made; Dodge, General Motors (GM) which makes GMC and Chevrolet, and there is Ford. All of these Recently Dodge and Ford were the most popular diesel trucks, but now that GM has come out with the Duramax they are all almost even.
There are many types of motors that these three companies have. Dodge has the Cummins. Until 1998 they had the 12 valve 5.9 L. Since then they have discontinued the 12 valve. From 1999 until now they have been using the 24 valve 5.9 L. This motor is decent, the only downfall is that it is more computer based so it is harder to work on for the untrained person. The 12 valve was pretty much all mechanical so somebody could work on it themselves.
In 2000 GM came out with the Duramax 6.6 L. This motor has more power than Ford or Dodge had so it became popular very quickly. Before the 6.6 L, GM had the 6.5 L which was strong but a slow and heavy motor.
Ford is known for its legendary 7.3 L Powerstroke diesel. This motor has been awarded many time for being the best in its class. This motor is well built and strong with adequate power. In 2003 Ford quit making the 7.3 L and came out with the 6.0 L. The 6.0 L was a good motor except for the few glitches that it had. My dad has owned two of the trucks. They are a great work truck. Although not as popular as the 7.3 L. For 2008 Ford came out with the 6.4 L. They have had quite a few problems with this motor already. It will be on the top soon though because of its twin turbo and its excess of power.
When looking for tires, you have many options. The size of tire you can get depends on the size of lift you have. Tires that are too large will rub on your fenders or leaf springs. There are many tire companies. I have listed a few.
Super Swamper is the leader in off road tires. The Swamper bogger is the most used tire for in the mud. Super Swamper also has the Irok, Thornbird, LTB, SSR Series, TSL Radial, TSL, and more.
Mickey Thompson is also quite well known for its Baja Claw. Mickey Thompson tires are great tires for a lifted truck that doesn’t go off roading to much. They aren’t to loud on the road. Mickey Thompson has many tires, a couple of the others are the Baja MTZ and the Baja Belted.
Maxxis has the Creepy Crawler. This is a very knobby tire. Driving with these tires can get annoying because they are so loud on the road.
BF Goodrich makes many tires. A couple of their more well known tires are their Mud Terrain and their Krawler.
Some truck owners choose to keep their stock rims when they buy new tires. Although many get different ones. Some rim companies are Eagle Alloy, Alcoa, American Racing, and Weld Racing. Just to name a few.
There are two types of lift kits. Suspension and body lifts. A suspension lift is where you put larger shocks or leaf spring that are arched more. A suspension lift can be as little as 3” but truck owners can get custom lifts of up to 20” or more! Body lifts are usually only 2 or 3”. This is where blocks are put between your cab and box and your frame, so it just separates it making your truck look higher, when really you haven’t changed anything. Some Lift Kit manufactures are: Pro Comp, Fab Tech, Tuff Country, Superlift, Skyjacker, Rancho, RCD Suspension, and Kelderman.
These days everyone wants to go faster and have more power. There are a variety of ways you can do this. All at a cost though. Aftermarket performance parts are quite expensive.
You can but performance computer chips which can give you up to 150 horsepower and 300 foot pounds of torque. Cold air intake, injectors, Intercooler, water methanol injection, renewed turbo, and exhaust kits. The list is endless.
If you got the truck and the money to improve it, be careful not to blow nothing cause of all that power. But have fun doing it if you do.