Hi! The Strato-Chief is a Canadian-built Pontiac, and uses the same frame/front end/rear axle/Engine and transmission as the -59 Chevrolet. The floor pans are the same too, both for the US-built Pontiacs and the Canadian ones. I bought mine from carsinc.com, but I Think YearOne and Classic Industries has the same products. I dont know if there is trunk floors available for Pontiac 59 that fits good, I made mine in 3 sections and made the stampings in a body shop. Try to find a Chevy 59 and look at the trunk floor, it might be the same as it is a Canadian.
Good Luck, Peter