A LOT of improvements in procedures AND materials in the last 40 years.
To give you an idea, in the mid-'70s, 500" Pro Stock engines made less than 900, gross, while The Professor claims they're making mid-1400s today ... a 50% improvement. See the current (June '13) issue of Hot Rod Magazine
for the interview.
No data given on whether the current version, above, has the Cross BOSS/Autolite inline carbs that are mighty rare today, but were worth some extra ponies, back in the day.