A tuner is a part of a radio. The radio is basically a power supply, a tuner section, an amplifier section, and a speaker. The tuning is accomplished with a variable capacitor (condensor). This consists of a series of metal plates separated by either air or mylar with every other plate fixed and the remainder attached to a shaft which can be rotated to increase or decrease the overlap between them.

That's about all I know about the subject. Good luck finding parts. The chassis will present a real problem. You will probably have to fabricate something.

Sounds like a fun project. Keep us posted on your progress.

Jeff