Motor mount question: Driver's side vs. Passenger side vs. Poly

[Steve]

I have a 67 Firebird/LC2 hybrid that I put together a few months back. When I built the motor mounts for the car I used a pair of new auto parts store motor mounts for a 86-87 turbo Buick and then I made the rest of the frame side to mount up the stock type motor mounts. I recently ordered a new poly driver's side mount from HR Parts and I tried to install it today but once a got the mount installed on the engine the frame side mounts that I made did not line up. The motor mount appears to be about 1/2" more towards the rear of the car than the stock type mount was. I suspect that the auto parts store may have gotten them mixed up and marked the mounts opposite so that I have a passenger mount on the driver side and vice versa. I talked to HR Parts and they said they would swap the driver's side mount I have for a passenger side mount(very nice about it, HR Parts def. a qaulity vendor!) so having them switched will not be problem if that is indeed the case. I just want to make sure that is the situation and that it makes a sense that they are swapped before I get them swapped and figure out its a different problem. If the sides are swapped will it cause the offset like I have? Thanks for the help.