Great job!!
Back in the early 90's I had a custom T/A I decided to dye the interior on.
I pulled everything out and first dyed the plastic rear side panels that were out of a junk yard and black. The rear panels are what started my dying it, I simply dyed them using a light blue interior spray dye they color matched to the other OEM panels/dash etc.. It matched perfect too!
The original rear panels were spray painted by cars original owner and the paint flakes kept flying all around inside the car as you drove it, man it was floating everywhere too so I had to tell passengers "keep your mouth closed"...lol I tossed them, so' don't just spray paint your interior, use the correct interior dye!
The combo cloth/velvet seats and my carpet I simply used several $1 boxes of Rit fabric dye on it all. I two toned the seats dark/light blue & died the carpet all black to hide all its stains. It still remained soft after dying, it looked factory except its two tone colors.
I won several 1st places with that T/A in local shows and on the track too because it was quick! I rarely ever made it through a drive through window without getting complemented on its interior because its two tone colors really caught your eye.
The only trouble I ran into was the seats had nylon thread running all through them so it wouldn't take the clothes dye at all. In the end its white thread I cursed the entire time dying it stood out nicely and gave the seats a real nice pop. Unless I told them nobody ever knew it was just a few of those dollar boxes of dye, it just looked so nice it floored people I told and It never wore off or faded in the three yrs I owned it afterwards. The guy I sold the car to totaled it about a week later in a street race, no surprise here, he couldn't drive a 4 speed to test drive it so his girlfriend had too.