DO NOT FIT!
These 81515 and 81514 seat adapters do NOT fit the factory bolt pattern. Not even close. if you are going to buy and keep his brackets, you will need to do major cutting and welding modification. After purchasing I am now finding my other buyers and reviews, that this is definitely an issue. I wish I would have read the reviews first I have also read that there has been many reports back to Procar about this issue. I do not believe they have made any attempt to update or make it correct. I am not sure where they got their original bolt pattern measurements from, but it was definitely not from 68 to 74 nova.