I would interpret what you have as 3.36 open rear end.
What Column 74 is I don't know, 75 either for that matter.
1968 400 Coupe, verdoro green, black vinyl top 1968 400 Convertible, verdoro green, black top 1971 Trans Am, cameo white, auto 1970 Buick Skylark Custom Convertible 350-4(driver)