Don't Believe the diagrams listed online there are a few that are wrong. The inner caps are numbered which makes it a no brainer as long as you remember The RH bank is 1-2-3-4, and the LH bank is 5-6-7-8
And, if I may add a note of advice... when you have the wires routed and the caps installed, check each and every one for proper placement and continuity before you install the assemblies to your engine.
I have a pair with wires, conduits, but only one cap, but I'm guessing I could figure out where the wires went on the side missing the cap. I'll see if I can check it out tomorrow night after work.
Every inner cap i have ever seen has numbers for both sides, they only have to manufacture one as it fits both sides. Sometimes you have to push really hard to make the plug wires "pop" into the bottom of the hole when it belongs.