The 1966 trunk mat was molded in a loop-style carpet pattern, like a rubber version of the carpet in the car. With solid edge boundaries molded in, too. New Yorkers got trunk carpet as standard.
The issues with a rubber trunk mat ARE real! If the rear window gasket does not leak, normal temperature swings can cause condensation to happen. Over time, it collects under the mat. When I discovered this on our then-recently-new Newport Town Sedan, it was easy to wipe out and the paint on that floor of the trunk seemed to be thicker than on the outside of the car. Had some air bubbles when it went through the bake oven, too, it appeared.
When I got my '70 Monaco Brougham, it came with factory trunk carpet as a part of being what it was. Simple black carpet similar to what was in the passenger compartment. NO rust under the carpet! Not a plasticized-back carpet, either. Plus a matching spare tire cover. Paint under the carpet was no thicker than what was on the outside of the car. PROVING the value of trunk carpet over the less expensive vinyl or thicker rubber trunk mats which came on the less expensive trim levels.
Seems like the trunk mat in the '66 Newport was a gray color? The one in the '67 Newport was black. Similar thickness and such. Downside was that it got stiffer and more fragile with age. Just the slightest flex resulted in breaks, unlike when it was new.
Perhaps the reason the Chrysler mats were thicker was to help decrease panel resonance from back there? Not unlike the factory undercoat did for the underside of the floorpans. The mat in the '72 Newport Royal was thinner with a different pattern on it.
IF the thicker trunk mats can collect condensate under them, so can the thick vinyl floor mats, too! Especially on the Fuselage cars with their (more common than not) leaking a/c cases. As the condensate would drip onto the carpet, it would normally seek the lowest level, which would be covered by the floor mats. Knowing about the leaking cases from our '72 Newport Royal, but seeing nothing of that on the darker green carpet in the Monaco, I was surprised when I pulled the rh frt mat up and found moisture dripping off of it. No coolant smells or feel, just "water". So, although everybody wanted "floor mats" in their cars to keep things looking new, there WERE consequences. I know the modern cars and their WT floor liners should be worse, I wonder about them in 30 years.
Personally, I would have NO issues with putting a nice black cut-pile or loop style carpet in any car which otherwise came with a rubber mat. Easy to generally find carpets in a smaller size or get one cut to size, then serged on the edges to mate OEM standards. Then mold it to the floorpan contours and then get a spare tire cover made to match. Might even cover the side boards, too. It would look good and help the car sheet metal back there last longer, too. Might not look original in all respects, but better overall.
Just some thoughts and observations,
CBODY67
