I’ve got a 1980 F150 with a 302 that I believe was swapped from a Mustang or at least we was told. It is far from stock I’m it has an aftermarket distributor I believe, the gauge cluster wasn’t hooked up when I got it and I don’t think it could be again. It looks like it only has a stock wiring harness for lights and such. I decided to buy some LED lights for the truck and see if it would work or not I’ve never tried them on a newer vehicle or older. I also bought a Kenwood Stereo to go in the truck. I changed all my lights except for my headlights which I held off on because of the issues I was having. I can get my brake lights and signal lights to work the running lights don’t want to burn very bright though, and there are no reverse lights but I think I just need a new reverse light switch because the transmission doesn’t look original either. Anyways the lights aren’t burning bright and with the radio if I turn the volume to a certain point it’ll turn off, or if I have the radio on and then turn on the lights the radio will cut off. I was thinking I may not have enough power? It has a 650 CCA 800 CA battery from rural king and I’m assuming the alternator is stock I don’t know how to tell that for sure. What could be causing the issues not enough juice on the battery or maybe the alternator? I’d like to get it fixed I have an electric choke Holley Carb and that seems to work fine once I’m sure I got enough power to run everything I’m going to add in the new Holley Electric Pump I bought.

 

My first thought is that changing to LED lamps as a diagnostic step is the wrong thing to do, this system wasn't designed for that.

It sounds to me like you need to... do a lot... I would start with verifying the charging system is working, go from there. Get the foundation working first, add the bling on top of that.