Cougar owners have been waiting for these for a long time! Rear interior panels in good condition are hard to find as most are cracked and broken with age. Repairing them is only a temporary fix and typically they will crack again any time you handle them. These replacement panels are the answer and if your vinyl is in good shape all you need to do is swap it over just like replacing backer boards on door panels. On my 68 with decor trim I found them to fit quite well and only I only needed to trim a couple small areas for better fitment but it was minimal. Test fit the panel before installing your vinyl so you can adjust fit as needed. You do need to drill the holes for arm rests and the decor trim so keep that in mind.
These seem to be a little more flexible or flimsy then the originals and I think they are slightly thinner in some areas as well. Not too much of an issue as it does not affect fitment but it does make it a little tricky to get the vinyl to nice and tight. Once you have the arm rest and decor trim installed it stiffens up the panel greatly. It took some time to figure out the best method of aligning it up before gluing everything in place. What I did was match the window crank hole first and align every else up via witness markings in the vinyl. These panels are almost an exact match as the vinyl lays down and lines up just like the originals. Use binder clips to hold everything in place then while lifting one side to apply spray adhesive to glue to center section moving to the rear section. At this point its a good idea to mount your arm rest to help hold everything in place and stiffen up the panel to help with keeping the vinyl tight. From here you can move on to the decor trim if needed then secure the edges with 1829 adhesive since it has a stronger bond then spray adhesive. Keep the edges clamped with binder clips over night and it should be good to go.
One other small fitment issue I had was with the window trim. It did not seem to fit the contour as well as I would like. This could have been an issue with the reproduction trim and not this panel but I am not sure. My original panels where broken to the point I could not compare the trim fit to an original panel to isolate which part was not ideal. I was able to massage the trim to fit better and not be as obvious. For pictures during the install check out.... https://classiccougarcommunity.com/forum/viewtopic.php?f=3&t=12525
Overall these are a great solution to a problem alot of cougar owners run into and what might seem like an expensive piece of modeled plastic consider what an custom upholster shop would charge to repair or recreate these. Or how hard it might be to find a good set of originals.