The Iranian Revolution began in 1977 after the Shah relaxed censorship against radical writings. By early 1979 the Shah left the country and died in the middle of 1980 from lymphatic cancer.
What if the Shah was able to keep a lid on things through a variety of measures, for example stricter censorship, and delayed the outbreak of revolution? It was probably inevitable once he dies and power is passed to his young son.
Given the same time scale, Khomeini's supporters would be in power by early 1982. The biggest impact this would have is the re-election of Jimmy Carter, and given Reagan's age, would probably be the end of his Presidential hopes.
Iran will be militarily stronger. They had ordered F-14s, F-16s, and Challenger I tanks. Only a portion of the F-14s were delivered when the revolution took place in OTL.