[joedoh]

if you look at the diagram, A and B are connected through a circuit breaker, with one important difference, A is AFTER the circuit breaker so you will be bypassing the protection of it if you use A for the batt instead of B

not having a P would just mean that your switch doesnt have separate front and rear park light outputs, some early cars likely did. front and rear park lights get attached to the R connection at that point. I used to be a car stereo installer (part of why I recognized the switch) and remember a few cars had separate park light systems, although mostly it was german/european cars with separate left and right park light circuits.