Not only new to A-bodies, new to MOPAR

Hello from Canada. Where do I start. I am new to Mopar. I have always admired the duster/Dart body style and finally have one. Here in Canada however some are a liuttle more rusty than others. I am not trying to build an origonal car, just build something fun to drive. I have a 75 Valiant, factory 318 front disc car from British Columbia ( Our equiv to northern Cali) I installed my first set of 3 piece headers ( aye vey) and been picking up stuff here and there to install in the spring. I am looking for a cheap OE radio. Be prepared for lots of beginner questions. Thanks in advance. Romeo