Back seat in coupe has a pull down arm rest that could only be found in a delux interior Zephyr coupe or sedan or continental coupe. The seat may need to be made more narrow for a Continental coupe.
I think I bought a rug kit for the trunk from an outfit in Florida by the name of Kepich. I don't have the address, but check the classifieds on this site or check through Hemmings.
As to cost, you get what you pay for. The average Continental starts at about $6,000 and goes up from there depending on leather or vinyl and details required.