Kelso is wearing a Clint Eastwood t-Shirt with the quote, "Go Ahead, Make My Day!". That quote is from the film Sudden Impact (1983), which wasn't released until late 1983.
The wrapper of Fez's Butterfinger bar is from the 21st century.
Donna introduces a new girl, whose father has an executive position with Six Flags. In the 1970s, the Six Flags Park closest to Wisconsin was in St. Louis, Missouri.
After they operate on $6 million Fez, they quote Spies Like Us' "Doctor, doctor, doctor..." scene, and that movies is from the mid-80s.