88 cutlass no power
 

Ive got an 88 cutlass supreme with the 305. It was sitting for a few years and I decided to get it going again. I got a new battery, changed oil and coolant. It started up with no problem. Now I’ve been prepping it for paint and have been starting it up for about 20 minutes everyday for like a month and have had no issues. Then the other day I had it running for about 10 minutes and turned it off. Nothing out of the ordinary. Went to start it 20 minutes later and nothing. No lights, no clicking, no power what so ever, nothing. Battery tests at 12.4 volts. Does anyone know where the main power relay is located. Or any relay that can cause something like this?