Spare Tire Bed Holes + Mystery Holes

[72FamilyBlazer]

1) Doing a forum search, I've found the spare tire bolts necessary are a 7/16 fine thread. upon inspecting the bed to see the holes I noticed the bottom right corner is significantly larger than the rest and does not have threads for the bolt to enter. Has this been drilled out?


2) Also, there's mystery holes in a peculiar pattern on the floor. Anyone know what these are for? They're quite small.

3) Lastly, there's two bolts on the right side of the bed floor. They look like they held something down, but I can't seem to find any pics of anything that would go in that area. Is this a PO add-on/alteration? Thanks all!