Radio heads are the control panels for the radios. In a small plane, the radio controls are on the front of the radios and the radios are mounted one above the other on the main panel. Appropriately, this arrangement is called the "radio stack". Airliners have more powerful, larger radios that are located in an electronics bay separate from the pedestal (or main panel). The radio heads in the pedestal allow the flight crew to conveniently select and read frequencies, and to set squelch and volume levels.
Building a replica radio head is in principle reasonably straightforward. All the earlier comments about front panels, lighting, switches, etc. apply here as well. You will additionally need to display numerical setting for your radio's frequencies. Typically these numeric displays are seven segment LEDs. These are, for the most part, widely available, in an assortment of colors, at low cost through the usual electronics sources. They can be interfaced through products such as the EPIC card. The EPIC card can also be used to interface the switches.
Blue seven segment LED displays are somewhat less common than the other colors. While certainly you can use blue fluorescent displays, LED displays can be a lot more convenient. Several years ago, Kwality Photonics Pvt. Ltd. in India. was apparently the only source, and purchasing from them could be something of a challenge. More recently, Lite-On Electronics has added blue displays to its product line. Lite-On products are available through Digi-Key.
White LEDs are available as well. One manufacturer is Forge Europa. I believe Farnell carries their products.