I had a look at them and it doesn't use a plate. The top is cast and machined for a specific router or series of routers to be bolted directly under it by the looks of it. Sears sold lots of routers made by Ryobi, anything starting with 315., and they offered tables and only the Ryobi made routers matched the bolt pattern.
To be honest, unless you are short of space, it's not a great idea to have saw and router in one. Table saw fences aren't made for routers because mist of the bit normally needs to be behind the face of the fence and there will be times when you need the full surface of the saw but you also have the router set for some operation that you don't want to have to reset it for.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.