open or closed V-Drive bearings

Changing some things around in my C-1000 which I'm sure has been done before in it's 50 year history so that got me thinking. It has 4 bearings in it. Two are 5308CF and the other two are 5308A's. Best I can tell they are all the same size just two are open on one side and the other are closed on both sides. The thing that stuck me as odd beside them being different is that the closed bearing are in the top of the V-drive. Would that make sense to have the closed bearings in the top?
Is there a reason for it beside someone just found a sale on the 2 different sets?
Are they interchangeable? Thinking it would be better to have all the bearings facing the inside to be open for better oiling?

open or closed V-Drive bearings