Purchased water pump kit RE62658 for my 5320. Kit included two gaskets that do not fit the 5320. I believe they are correct for the 5420, however I can't find a breakdown on JD parts of what part numbers are included in the kit I bought to know for sure. They look like they match the 5420 water pump on JD parts.
Anyway, if someone would like to have them they're yours. Just let me know where to send them.