What/how many parts are needed for entire Black interior conv.

2 kick panels
2 door panels
2 door handles
center console (armrest, lower console, upper ashtray console)
2 interior quarter panels
1 rear center metal plate (connects 2 quarter panels)
2 rear hatch panels
fuse cover
steering column cover (lower part)
lower dash

I belive those are all the hard parts of the top of my head, now you'll just need a black carpet.
glove compartment door

If it is factory black, then it is a 90 or newer interior. The dash is diferent, so the fuse box and steering wheel lower cover are replaced by the knee pad. Also the AC controls have different mounting points. The dash shell itself is painted black so you should get the complete dash with all the AC vents and dash pad. Also you need:

2 door sill plates
the piece on the hatch itself
all the seatbelts (they will be 3 point belts in the rear vs lap only belts, but you can make them work.... I did )

You will have to drill new holes for the front seatbelt top mounts as they were raised up a few inches in 90 vs 89 and earlier.

headliner and maplight,
cargo shade,
sunvisors,
visor clips,
coat hooks,
all the armrest plugs,
console hole plugs,
shock hole covers,
rear carpet,
and of course, seats.

I do have a few of the little parts that I've collected, so if you need something, let me know.

Thomas

Total PINA so I mixed and matched my 89 car with 90 black
I would spray the 89 sides to match.

The dash is a easy swap, CHANGE the heater core while there !!!