The early 8 bolt stuff was 1018 and when Scat got the MP contract everything was 4340. I’m not sure MP ever offered a crank in 5140 but I’m not sure on that.
What about around 1977 to 1979 what material was used ?
Mine is a 3.20 stroke 8 bolt flange Bob Glidden crank I guess he used Mopar Stock but mine had chroming process installed which I was told was very expensive back in day ??