Okay, I just completed recovering my 68 Coronet bucket seats; new canvas and foam as well. Just to document everything for others, here are some pics and tips.
1. Prep your seat frames by wirebrushing, sandblasting, and painting. Remove all the old hogrings.
2. Go to Legendary Auto Interiors and watch 1968-1969 A & B Body Foam Preparation to see how to attach muslin to the foam (and foam to foam on the seatback).
3. Attach burlap (which is not provided in the kit from Legendary; I used canvas tarp material) to the top of the seat bottom and seat back following the instructions in the video.
4. Use spray adhesive to attach the muslin (which IS provided in the kit by Legendary) to the foam. I used Gorilla brand.
5. Insert the cardboardy-plastic insert into the back of the seat back following the instructions on the video.
6. Reattach the plastic headrest slides. (I believe the later 68s -- those sold after 1/1/1969 -- required headrests.)
7. Hogring the muslin (and by extension, the foam) to the seat bottom and back following the instructions on the video. The point is to prevent the foam from moving around while you attach the seat covers. Note that I had no stays/listing wires to worry about on these seats; other seats may have stays/listing wires that you will need to attend to. (If you're like me and dodn't know what they are, stays/listing wires are used to attach the seat cover directly to the seat wire through a cut in the foam. There's a wire in a pocket in the cover that is hogringed directly to a wire in the seat. They add shape to the seat bottom and/or back.)
8. Cut the foam from around the headrest slides to prevent bulging.
9. Go to Legendary Auto Interiors and watch 1969 Dodge Charger Front Bucket Seat Cover Installation to see how to attach the seat covers to the seat bottom and then the seat back. (Tip: the order of attachment is important to ensure wrinkle-free installation and to prevent tearing.)
10. Hogring the seat cover to the seat bottom and then the seat back following the video instructions.
11. Attach the seat back to the back of the seat with two screws at the bottom.
Tips:
1. Be prepared to pause the videos often so you don't miss a step. I had never done anything like this before, so I took my time.
2. Learn how to use the hogring pliers; there's a technique that results in more good fastens and fewer mis-fastens.
3. If you mis-fasten a ring, don't be afraid to cut the hogring and try again. My most used tool was my wirecutter.
4. I don't think the Legendary kit came with any hogrings (it might have but I don't recall). I bought two hogring pliers/rings kits off of Amazon. The kits included smaller hogrings (perfect for attaching muslin), larger hogrings (perfect for attaching cover/piping), and even some larger clamps (which I used in a couple of the corners where I had a couple of pipings and a larger reach to the seat frame.)
5. It was suprisingly easy and the results are surprisingly professional looking!.