X 2 with vicrod.
the stock manual lever position switch for the 4L60E only has 3 inputs to determine gear position/selection.
The scematic shows 3 wire with a gang of 5 switches, which makes it interesting.
I have a schematic , It may help you, or confuse you?
I do not have any way to tell what combination the switches will be on or off in any particualer gear.
An aftermarket setup for you indicators may be the way to go.
Fords MPLS are a little different , at least from what I can tell from the schematics.It has a series of different resistor strips, and each one has a tap, so the value changes each time the selector is moved to the next gear.
I suspect the GM MPLS has resistors in it, allthough the schematic doesnt show it, but 2 switches on one circuit to be in parallel does not make sense, it would be either on or off. It only makes sense that the GM switch also has resistors in it. I just have not had the pleasure of tesing one against a schematic. Even if I did , I am not sure it would help you configure a setup to run your indicators.