Brake lights, taillights and turn signal wiring diagram needed?

Wow, an 87, those use a box standard GM wiring system. Brown are the marker/plate and parking lamps. Light Green are the reverse lights. Yellow is Left Turn/Brake and Dark Green is Right Turn/Brake. Black is grounding for all lights.
FYI you cannot split the turn signal and brake lamps in the rear. They use the same circuit for both with the turn signal switch determining their function. You would need to do some alterations if that is your plan.