All the GFS stores that I've been to only sell the giant cans of 6 in 1's, which I don't like to use and find storage of the unused portions difficult. I like the smaller 28 oz. cans of 6 in 1's and either order direct (shipping at 25 cents a can is dirt cheap) or find some at local Italian deli's (which you'll have to search out).
When I first went into the deep dish style, I used 6 in 1's successfully, but then when visiting the classic deep dish pizzerias I noted my replicas lacked some of the more chunkier tomato pieces, which really enhances the deep dish pizza experience (even tho I don't normally like chunky sauces). So I often found adding some chunky dice pieces of tomatoes, like from Glen Muir or other good brands, along with the 6 in 1's to be really good. FWIW. --BTB