Finewhether,
Sweet cherry and sour cherry belong to two different species so usually "no it won't work". However in "this" case sweet and sour cherry "ARE" recommended pollinators to each other. But you still have to go about carefully selecting the correct varieties just as you are doing because there are still very important considerations;
(a) bloom overlap,
I have seen a cherry graph of bloom times with Kordia cherries which are later than the average period of time in the spring. I have also seen this late bloom on Kordia at orchards at high elevations in The Dalles OR which were later than other varieties there so I think you could trust that data. By the way I love Kordia cherries.
-Just make sure that your choice of pie cherry pollinator is also late or has sufficient overlap.
(b) compatable pollen,
Some cherry trees may not be able to pollinate others because sweet cherries are classed belonging to pollen groups. It gets involved but generally trees in one group can't pollinate others belonging to the same group. Many sour cherries have this same problems with groups. Even recent research at MSU they are classing sour cherry into various classes. As a result many sour cherries now belong into the same groups that sweet cherries belong. Even more complicated is the fact that sour cherry varieties can belong into two cherry groups making it more likely Monmorency is even less likely to serve as a pollen source for Attica. (know you didn't want to hear that) Fortunately MSU has put many of the common pie cherry selections on the internet recently so that farmers and people like you can make informed choices.
-Ask again and when I come around here seeing the question again I'll see if I can find you the MSU link on the information.