The 1970s yes the anabolics changed but the 80s they're the same. In the 80s the anabolics were even better than now because everything was pharmaceutical grade back then, parabolan which is pharma trenbolone was in the market, the famous syntex anadrols etc.... Lee Haney was the biggest guy around back then at 6ft 250 on stage. Right now Nick Walker is 5ft7 260 on stage so the question is why guys today are bigger?
Dorian was the one who began the mass monster era in 1993 where he made a big jump in size. From that year forward we started seeing mass monsters like Nasser, Jean Pierre Fux, Markus Ruhl, Jay Cutler, Ronnie Coleman and many others. The only thing that has changed from the 80s is the addition of gh and insulin. The reason I say anabolics are the same is obviously because there were abusers in the 80s who used big doses but were no where near the size of the guys we see today.
Training is the same, even the old timers always say they were training harder than guys are today, which is obviously and exgarration and guys in both eras train very hard. Food is almost the same, it's always been high protein high carbs from the 80s and early 90s forward.
Genetics is an interesting topic, because in that era that top guys obviosly had a much better genetic blueprint for the sport than now. Look at the natonals in the late 80s and 90s with guys like Coleman, Levrone, Wheeler, Cutler, Branch Warren, Matarazzo, Shawn Ray and many others who are all Mr Olympia caliber. But you have guys like Lee Labrada and Sergo Oliva whose sons are now bodybuilders with much more muscle mass.