Been involved with a few of these over my many years.
First step will be to find an excellent trim shop. If you’re close to WI, one of the best is located here.
The orange plastic parts [seat trim, door panel trim, wind lace] were molded in orange and can only be re-dyed. These parts are often missing and can be hard to find.
Black plastic parts [kick panels, console, seat belt covers] can also be re-dyed. I have never used them, but I have heard the reproduction kick panels are excellent.
The instrument cluster is a different, harder plastic that is likely brittle after 54 years. If it has not been hacked for an aftermarket sound system and the wiper switch mounting tabs are intact, carefully clean it. Don’t attempt to paint it. If it is damaged, an excellent repro is available.
If the dash pad is original, it is probably hard and warped. Trying to straighten and glue it is a waste of time. Again, excellent repros are available; best of the selection is the OER. Also, the most expensive; you get what you pay for.
Z11s had custom seat belts with brushed chrome covers. If they have rusted, you will have to find replacements. If the labels on the webbing are intact, they can be hand washed. They are seat belt restoration services available if the webbing is damaged or the labels missing.
The front seats will likely need to be completely rebuilt. By now the covers are faded and worn. They will tear during removal; the seat foam will disintegrate. If the seat frames are rusted, they should be stripped. The drivers seat frame may be bent; I had one with broken welds.
Rear seat usually in better condition, will be faded at minimum. There are only repro seat covers. The houndstooth cloth used is not an exact match to OE but very close. The buttons on the repro covers are not exact but the buttons from the originals can be re-used.
Not much you can do with the headrests; they were molded and are hard by now. There are repro covers, think sore thumb.
Rebuilding the front seats is best done by an experienced shop. Getting the foam and covers on correctly, pleats properly aligned, is hard work. One bud paid close to $1,000 just for the labor and they looked like new.
Original molded door panels can be recovered with new vinyl; think Al Knoch does this. I have not heard anything good about repro panels but there may be better ones available. The quarter trim panels usually can be re-used, probably reproduced. Top boot is reproduced if you need one.
Everything else [carpeting, sill plates, cranks, ash trays] is easily available.
