If you have rotatable nocks, then it doesn't matter which indexing unit you use, because the only difference is how a fixed nock would be positioned relative to the fletching. If you use a left index with right wing feathers (or a right index with left wing feathers), then all you have to do is rotate a press-in, rotatable nock a few degrees to get everything lined up. Since you have a right clamp and right wing feathers, you are set to go, unless you use fixed, glue-on nocks. I like the 90 degree spacing best for 4 fletch too.
Allan