Lemans info

Hello
New to this and finally saved up and bought one. It’s a 1968 conv lemans. I was trying to do some research and find out what was original enGine and Tran in the vehicle. I know very little about this car so any help in starting off learning would be appreciated
I know it has a 350 two speed in it now. I think it’s the original rear end but not sure.
Where are the numbers and how do I know if that’s what it came off the line with.

Thanks
Scott