I got a Viking quilting kit for my Designer I. It had an extension table and several feet. The walking foot that came with that package was the older original version, the one with the fixed base plate, which I used for years. Eventually I did get the newer foot with the interchangeable plates. I will say that it was very expensive, but I do use all the plates. If you are going to do a lot of SITD, that plate is wonderful.
CK's comment about the even feed vs. the walking foot operation was intriguing. I'm going to my dealer today and will ask if they make an actual even feed. I'll let you know what she says.