Installing OEM smartcard reader; question about model numbers of bottoms

I've a Latitude E5520. I'm looking to replace my PC card module with a smartcard "SC" module. It appears to be a FRU. There are some OEM modules (readers) on ebay; moving on: I've had some problems with sellers not being able to tell if the base bottom--which i need to replace to fit the new module--is the SC version. Most just don't know even if I send them a picture. The board is listed by several different sellers with varying five character identifiers such as OM6MH. I don't know where they are getting these identifiers from. My concern is when I finally get a positive hit on a "SC" board, there might be some other differentiator which will prevent a smooth replacement. I bought this latitude used from dell, but other than the difference between the card slot (EC, SC, PC), I don't see any noticeable features which might prevent a smooth bottom base swap. When I get a hit on ebay for a smartcard version, should I just disregard that model number, or are there more differences which will prevent the swap? Thanks.