Bryan, does the seat kit fit over the existing covers or do they have to be stripped?
You need to strip off the old covers; they're only mostly contact cemented on, and you carefully peel the old covers off, paying attention to the edges where you may (will) see that the factory was not precise with how they put the contact cement on the cover. If necessary, I've used 1/8" thick padded headliner (not here, but on 693R when I did those seats) to repair the side padding; the bolster padding is a bit more resilient.
There are 4 rivets (at the insides of the seam runs to the inside and on the back--see the photo) that have to be chiseled off (real simple, sharp chisel, good whack or two with a hammer to the tail and a punch to drive the head out) to release it. The headrest is attached with 4 rivets through a fiberboard mount at the top (again, whack carefully) and the rear trim piece is those infernal screw/nails into a plastic anchor. The kneepad is 4 rivets on the bottom, and the backrest is 6 poprivets to the metal frame.
I make up small aluminum plates to hold the rivnuts where they will be used on the fiberboard instead of pop rivets; some JB Weld epoxy on the back, couple of #6 1/4 inch wood screws to attach to the fiberboard on the kneepad and backrest with the rivnut set into the old rivet holes. The holes for the rear trim cardboard (which I paint) and the headrest mount, I shoot rivnuts directly into the seat frame; they're chromate plated, so will ameliorate the dissimilar metal issue; you can get steel nutserts, but they're more expensive, and I have a copious supply of rivnuts in my hangar, so they're my choice.
Then, it's fiddly fitting, cutting, stretching, contact cement, pop rivets for the seam to frame...next time, with the fact that it seems I ended up with a couple creases since I started at the nose of the seat and worked back and up...I'd try riveting the 4 seam rivets first, then work out to the ends rather than how it did it this time (which left a creases at the bottom where the bolster goes up the side...) oh well, adds character, right?
I replace all the rivets that are visible with countersunk stainless machine screws (depending on the size of the rivnut) into finishing washers on the exposed surfaces. Yes, I paint the frame with gloss black rustoleum after a spit coat of rust neutralizing primer. It's hidden in most cases, but I know it's there...
It just takes time and patience. With the cost of replacement covers from the UK (including shipping, came out to less than $275 USD delivered, which is 50% of what some folks are charging in the US last I checked, and are probably getting it from the same source!) and some sweat equity...it turns out just fine (second photo).
FWIW, the headrest and kneepad/bolster were in good condition; I didn't use the cover parts from the kit (they're on the shelf in case I need them someday); so just redyed them when I did the seats (I didn't redye the back or butt pad; you can't tell the difference). Full disclosure, I used the SEM vinyl primer/prep and satin black spray to do the redye; I've had good results with that particular system...on both cars and my Cessna interior...)
I was careful with removing the backrest and butt covers, and have one bolster (they're mirrors of each other) that's not damaged; if someone wants them to bring to their local shop, or has the skill to sew up using them as patterns, let me know and I'll put them in a box for the cost of shipping...I don't need them anymore...
For a driver (not a garage queen or Pebble Beach entrant), I think it came out just fine...not perfect, but certainly a lot better than split seams and stuffing showing. And...with the new carpets...you get a 'new car smell' whiff as a bonus!
HTH.
