Sorry this has taken me so long but I was trying to find someone with knowledge of the original rear floormat material in Advance Design Suburbans. No luck. So, I contacted Battle Ship Linoleum (Tony Lauria, 610-268-3441).
http://www.battleshiplinoleum.net/ The good news (for brown/beige mats):
Tony was not certain what material was originally used in Suburbans but he kindly sent me samples of his products and an article from "Woodie Times" about putting grooves in his product in a restoration of a 1951 **** Country Squire "Wooie" ('49-51 were similar models). The sample (with grooves that were routed by one of his customers) is light brown (dark beige) in color and the material thichness is a good match to my mat (0.125" : 3.2mm). The routed grooves almost perfectly matched my mat.
The bad news (for black mats):
My 1954 Suburban has a black mat (earlier Advance Design years were light brown, I think). Tony does not carry black mat in 0.125" thichness but he carries it in 0.100" thichness. This thichness is thinner than the mat in my 1954 Suburban and it is probably too thin to rout.
I am fairly certain that Tony's mat came from Armstrong and I have contacted Armstrong to find out if they have any more 0.125" black material (they supposedly stopped production/importation last March of this thichness in black). I will post any information I receive.
If you are interested in the brown material, it costs around $5 per square foot and the AD Suburban's mats are approximately 62" x 82" (5x7 feet = 35 square feet = approximately $175 plus shipping). You will have to rout grooves in the material but Tony will send you a copy of the Woody Times article (it is very useful).
Please note that I have no knowledge of the rear mats in earlier or later Suburbans (or station wagons or panel wagons).
Tim