What I did, because I'm cheap, and have a drawer full of extra sockets. I took a 1", deep well, thin wall socket, and drilled a hole near the top, to put the wires through. Then ground a notch to tape the wires in to keep them out of the way.
I had to make the end of my socket thinner to get it down in the head.
So far, on the ones I've changed out, I have not had to remove the rocker box.
After it is installed, you can take a piece of stiff wire, to fish the wires through the hole in between the heads.
Then I use a small amount of KY lube on the inside of the rubber cap to get it on, use the stiff wire with a loop on the end.
