Dan, very nice car/rust free body to restore!!!!!
Did u get a rear trunk finish panel with the car? If so is it silver with fish emblem, or black with round Formula-S emblem?
There is NO way to tell 100% what the car was without the fender tag or build sheet. Could be a 340 non-S, 340-S, or even a 340 'cuda package!!!!
Standard rear would be 3.23, the 3.55 and 3.91 was an option, but 4.10 never was. A factory 3.91 gear car is very rare and would be more likely on a 4 speed if at all. 3.91 was only available after a certain time?(i have a factory sheet stating this).
looking forward to more on this car/post............