I would think earlier versions should be okay. Typically speaking the two letters at the end of a part number denote revisions, not necessarily new designs. It could be something like a material change, a vendor change, etc. but the vast majority of companies only revise parts if they are backwards compatible, so any part with the same number can be used in any installation. If a revision would mean that it can't be used in an older car, it would get a new part number.