It shouldnt be too hard. If you hunt around you should be able to find a thread where I put late model seats into my mustang. Oddly enough Ford kept the width of the rails consistiant from 65' to at least 04. I had to modify them so that I could bolt them in the way the 65's originally did, but it wasn't too hard. I didn't use power seats though, they may have set higher than manual seats. You will want to modify the pan the seats bolt to and lower it down, otherwise latemodel seats sit way too high. Here is a good article for that:
Mustangs Plus - Tech Articles - Lowering Seat Pans (Page 1)