Got the truck outside so I can get to it from both doors.
With the passenger seat mocked in, I could tell where my bolt studs poked down and that would tell me where I needed cross pieces with holes in them for my studs to poke through.
I was able to sit in the seat at this point and adjust the recline angle that would work at a driving position.
Also important- I measured each seat and ran blue painter's tape down the exact middle of each seat.
I also ran tape down from my glove box button and the horn button. This was to mark where the center of the seats should be in relation to the truck. I wanted these things to feel right, not like they were some hacked-in wrecking yard seats out of an import!