There are several things to consider when upgrading the head unit in your truck. You will first need to identify the size of the opening. The height of the unit determines whether you can fit a single-DIN (2-inch) or a double-DIN. Many older vehicles are of a single-DIN height so it is important to check the maximum size that your truck can handle.
In addition, the installation of an aftermarket stereo will require a vehicle-specific mounting bracket and wiring harness for the speakers.
One feature to look out for when shopping for a new stereo is Bluetooth. Bluetooth is a wireless communication standard found on nearly every phone. Once a rare feature to find on a head unit, it is becoming increasing popular. If a stereo features Bluetooth, it means you can connect your phone to it to make and receive phone calls.
If you plan to get a lot of use out the hands-free calling, you will want to avoid a feature called "parrot" Bluetooth. This means the system only sends the audio of the phone call through the speaker and relies on the phone's microphone for voice input. The ideal setup is a unit that has an external microphone that connects to the unit. You can then place the mic in an ideal location for picking up your voice.
Another feature to consider is whether the stereo has a detachable face. This feature goes a long way in avoiding theft. It allows the front of the stereo to be removed and taken out of the vehicle. It deters would-be thieves because the stereo will not work without the front of the stereo in place.