im sorry dont take this the wrong way but why on earth would you buy something off ebay and then ask questions later?? you are supposed to ask before you buy anything of ebay. but to answer the question yes they are both the same and they will fit your mark VIII, the air has been let out of them thats all, once installed and aired back up, they will both be the same size.
As far as I know all air-ride related parts are interchangeable with all years. The newer design of 97/98 front struts seem to be the preference though but they are still all interchangeable.
Installing rear bags is really easy. I just did mine. New $200. How much you pay for these?