i have this:

It tells me what systems go where, but not which end of the system. does it matter? for example, the cross car wiring harness for the power windows plugs into p or r? does it make a difference? thanks for the help.

If your asking if it matters between left and right sides, it makes no difference.

not so much left or right.... but, still using the power windows as an example, there are two pink wires with a blue connector that run to this block. One comes from the cross car power window/lock harness and the other is in one of the huge "everything seems to run through here" harnesses. which one goes into p and which one goes into r, or does it matter? I'm thinking that it doesn't matter, but I don't want stuff to go zzzzzzzzap on me.

I'm thinking you would need the specific wiring diagram with each system (circuit number) to be absolutely sure. Trace where the wire comes from and where it goes to. If one wire needs a different amperage it may matter. But I am just guessing......

ok so I looked at one and i see it is nothing more than a junction block, and they can go in either position.