Will connecting rod caps on a 350 Chevy fit in either direction?

NO! They have to be installed a certain way. If you have it on wrong it will actually be quite obvious. Keep in mind the bearing notch has to prevent the bearing from spinning in the same direction as the body of the connecting rod does. Install the cap so the bearing notch faces the same direction of rotation as the rod body does. The sides of the connecting rod are thrust surfaces as well. Install the cap backwards, and they most likely won't match up either.