Brake lights ???1984 chevy 6.2 diesel pickup

I just bought my first MV last month. (6.2 Chevy diesel pickup). The blinkers/ brake lights were not working. I replaced the bulbs and now the blinkers are working but the brake lights are not. I'm sure you guys know both lights function using the same bulb. What should be my next step in getting them to work?

Change signal stat flashers. should be 2 (in fuse box), check ground connections also.

Check the stop relay switch on the break pedal and have someone press it down while someone looks at the tail lights.
If it works by holding it down, re-adjust the stop relay switch.

Check the fuse, check for corrosion in the fuse block, and another very important item to check is the ground strap/tab inside the lamp socket, check all of them. I had an issue recently where they looked good but were actually cracked and not making contact.Also, use a die-electric grease to prevent further corrosion.

THANKS

Thankyou all very much. I'm headed to the truck to try your suggestions now. I'll let you know how I make out. Thanks again for your prompt responses.