Headliner and Carpet:
After a quick stint at an interior shop, made some substantial progress in the past couple weeks.
Had them install a complete carpet kit from GAHH, which by all accounts went in smoothly with no issues, and the final product looks great and extremely close to the remaining pieces of the original brown carpet that came in the car.
Additionally had them install a Coupe King headliner kit. The original cardboard/fiberboard reinforcement, so they had to rebuild a new one (no pics of this). I used black MB Tex vinyl from GAHH for the A and C pillars. Also, thanks to a tip, I am in the process of refinished some of the headliner slot edge trim with SEM Ranger White vinyl paint.