Springs

Ok guys I have a question for ya. I own a 78 bronco, and a recently put a lift kit on it, once I did this I noticed my springs were saggy in the back. I was wondering how wide are the leafs in the back of a 87-96 f-150, they seem to sit higher than the older f -150 in the back and I was thinking that I could swap these in. I am also going to haul a trailer with sometimes a race car or any other car for that matter, so they neeed to be a little beefed up too. THANKS IN ADVANCE