Yes, and yes. Up until maybe 20 years ago, an 8' bed was an 8' bed and toppers/shells were pretty much universal. Recent trucks probably take a topper/shell specifically made for that model and year. A topper for a 1st Gen Sport Trac won't fit anything else, and vice versa.
I checked Craigslist every day for a year and a half before I found a topper for my '02 ST five years ago. Found 2 in the same week for my '01 this last spring. I have a factory hard tonneau and a flat 1 pc hard cover I'd sell, but I'm in Iowa.