OK I got everything installed today. I need to get back under the truck with cable ties.
1) The reason I didn't want to use the backup lights was that this way I can use it with the lights off, tho the truck has to be switched on.
2) If there are stubs for the upfitter switches next to the engine compartment firewall, I couldn't find them. But there is so much gear stuffed in there that you can barely see the firewall. I used a ladder and looked down but could not see them. The master cylinder shown on that drawing looks like it comes off a Ford Escape and bears no relationship to the very large one on the 350 with it's volleyball sized power boost.
3) So I ended up pulling up the rug and running the wire up into the driving compartment. Works fine.
Thanks for everyone's suggestions. This turns out to be a nice little led strip, really seems bright. You mount it by some 3M tape and just stick it where you want it and it has a switch. A tad pricey at $40 delivered.
Glendale Titanium 29E34TS fifth wheel
2012 Ford F-350 4WD Lariat 6.7L
PullRite OE Series Super5th 18K