Whew. A lot to learn but I'm gonna give it my best shot. First is the shape. Like many factory pieces these soft parts from back in the day were just a crude fit utilitarian piece. Never intended to be a show car piece. That being said I'll try to straddle the line of correct OEM shape and maybe minor tweaks like I've done to my gaskets for better fit/coverage.

Couple question / insights so far.

1) What years, makes, models had the tan plaid pattern (like shown above)? Looks like 68-69 A an B bodies so far but I've read online some 68-69 B owners had gray plaid. Was it just whatever was available from the vendor or was it a certain plant.

2) What years had the dark gray PVC foam backing? I know 71 E bodies for sure. And just received a 72 GTX mat from a local guy that also had the foam backing. These mats were also made from a material called Burtex. The company, still around, makes burlap based fabrics. Not sure if they printed the herringbone pattern on the Burtex or if someone else did that. I still need to call and find out. Looks like other some other big name interior companies sell this Burtex material. I'll buy a chunk of this (and their vinyls)to verify its accuracy

3) Burtex, what years, makes, models used Burtex. It's a light weight, fleece backed material with a dark gray PVC foam. Ford used this in the 60's and 70's also. If you know your trunk may is/was Burtex I'd be interested.

4) It looks like some mats have about 6" sewn on to the part that goes up to the back seat. Wonder if the rolls only came in a certain width (appears that may have been like 54 or 56") and the piece sewn on was necessary to get the extra length to cover that area upto the seat. Met a guy with a 64 Fury last week at a car show that said he bought 2 mats so he could cut a strip from one and sew it on to the other like the factory did.
What mats had this extension?

That's a start

Jim Fillmore