In-bed Spare tire mount on ‘84 k5

[Newtynewt]

Hello all. I’m hoping someone could post a couple of pics, actual or diagram, of the mounting of the spare tire carrier with tire attached. Two most curious points:
1. How does upper arm attach. It appears as though the upper arm mounts to the rails area but right at a bolt hole that would hold the top. Not sure how that works
And
2. I’m missing the plate/bolt that would fit over inner wheel. So what do I need or what could I use in place of if I’m unable to locate that hardware. Thanks so much. I’m looking forward to getting this mounted if only for the look of it. Pretty badass looking indeed.