Are the frame engine mounts the same for a BBC and SBC for 1st gen?

 

No, they're different. And the 69 brackets are different from the 67-68 brackets.

 

they will both work, but if you use SB in place of the BB brackets, the engine will be placed a little further back and to the driver's side of the car. this really isn't too much of a hassle unless you have power steering AND big tubed headers. just don't ask me how I found that out