As you are taking off the panels and such, keep a list of the missing screws. For instance, if you take something off that is supposed to be held on with 4 - 6mm X 10mm washer head screws and two are missing and one of the others someone jammed a 1/2 X 6 wood screw into, make a note to buy the three proper ones. It will save 47 trips to the hardware store when you are trying to put it back together and will eliminate the temptation to put that wood screw back in "Just for now..."
Take the time to catalog those screws, fasteners and other things that are missing, broken, marred, or just plain old needing replacement. Then either get them from a bone yard, MotorSports, Victoria British or a good body shop supply house.
The rivets that FantaZ mentions are notorious for losing the little plastic spreader pin. You can buy new ones, but if you take care you should be able to find the pin and re-insert. Or if you are obsessive about reusing the originals, figure out some way of pulling them out via the front. Whether by using a pin, glue, or drilling and tapping a real small hole then using a screw, and yes you can find screws that small check your local radio control hobby shop.
Also take care when removing the vinyl from your transmission hump and the rocker panels. If you do it right there's no reason you can't clean it up and reinstall the same pieces.
Once you have the new floor pans in, make sure they get protected both inside and out, then get some sound absorbing mat material, "Dynamat" is excellent but expensive. Check Eastwood they have a couple types, so does Motorsport. Someone has reported having used POR-15, another the pick-up bed liner spray on stuff. Either way, you want some sound absorbing material there, otherwise you will regret it.
Once the interior panels are out, if you are going that far, take the time to spray some sort of rust inhibiting paint or coating on those areas of the steel that are not normally protected well. I'm talking of the inside of your doors, kick panel areas, rocker panels, behind the plastic pieces etc. You won't regret this.
What they say about plastic rivets is true. I got so pissed when I lost almost every single one of those damned pins - especialy since the car was parked on foot high grass, which made finding them like trying to find a pin in long grass! The true enthusiasts may not agree with this, but I just bought a jar of nails the right diameter, and hacksawed them to suit.
Be careful removing the vinyl walls in the rear. They bend arround 90 degrees from the rear of the car to the sides. Your going to have to bend them in on themselves to get them out of the corner, and if the plastic has gone brittle with age, this can be a problem. I put small 1/2 inch cracks in mine trying to get them out. Thats when I had to learn plastic welding.........
Just dump all those stupid pin-style panel clips unless you are doing an authentic resto. Mine had a bunch of them and I am a freak about rattles and I went to great pains to NOT LOSE ANY of those &%)($#& pins inside the body somewhere. Replace them with one of two main styles of removable panel clips which are readily available at NAPA. One just has a flat head that sticks out and you can easily pop it out with a putty knife or pliers. The other has a fake Phillips screw head that will not actually 'unthread', but pops out reasonably easy. You will have to drill the anchor holes in the metal out slightly to 1/4"--which will make purists cringe. The old holes are not quite large enough to allow the back to properly expand and you will bend or break the tabs. (This is the only SAE switch I have made on my car.) And you don't need to buy Datsun specific door panel clips. The NAPA 665-2057 works perfectly for the wood-backed panels at the doors and behind the seats.
In case you have not searched the archives on this matter I would HIGHLY reccommend re-finishing all your panels with Krylon's or Rust-oleum's Vinyl Paint. Just wipe everything down with a fast solvent and spray them. The stuff is so thick and tough. One coat makes them look brand new.
How does Krylon's or Rust-O-Leum's black or satin black or whatever color you used match up to the original black color? I have a couple white panels that might be made useable if I paint them.
Only note I have on your procedure, when you said fast solvent I would caution tvzdude and others that some of the plastics will react pretty violently with lacquer thinner, M.E.K., Acetone, and you will actually melt the top part of the plastic and mar the "leather" finish. I personally use denatured alcohol to get rid of the bulk of greases and other stuff, and I'm not opposed to good old plain soap and water if I can get the piece out of the car.
If you do use a solvent, use it sparingly and quickly.
I did several tests on the back of a panel because, quite frankly, I thought the vinyl paint ws probably junk and would peel off or not be flexible enough. I tried Laquer thinner, Acetone, and Denatured AL and ended up using DA. The LT and Acetone just 'solved' the plastic too much, as you suggested. During my tests, I took a knife and fingernail and sandpaper to the paint to see how tough it was. I was VERY surprised at the results. I also sprayed it on a piece of soft vinyl and bent it repeatedly. The paint not only 'solved' to the surface doggedly, but resisted scraping and did not show any stress on the soft vinyl. Note: I used only the Krylon product and have never tried the Rust-o-leum. As far as matching, Black is black, and the only difference is the original panels and vinyl are dull and scraped and 'light', and the sprayed panels are dark, dark black and glossy and 'deep'. I did all my panels and vinyl, so I did not have a match problem. The only thing that does not match is my brand new Victoria's Secret full dash cover, which, even though it is brand new out of the box, is not as rich and glossy as the sprayed panels. I think I will leave it that way though. It isn't noticeble at all and as well as the Krylon performed to initial tests, I am hesitant to subject it to the rigors of a dash. Also I hate to paint a brand new product!
In order to get that nice glossy deep look to it don't use Armor All. Use Clear Guard by Turtle Wax. The difference is dramatic, it lasts a long LONG time and doesn't leave an oily film that evaporates eventually and fogs your windows.
Thanks for the input on the paint. The reason I was asking on the match, is that I've found that you can usually get a good Vynil cleaner and then Clear Guard and it's almost better than painting, but there are times when the sun has baked part of the color out of the top layer, and then painting restores it.
You say it also fills well? I wonder how it would do on those annoying little cracks on the center console that seem to grow out of nowhere.