Finally succeeded at installing a set of rear seats and seatbelts from a 2000 truck. Mine had no rear seat or seatbelts when I got it.
I thought I had to tap all the holes to mount the seats and seatbelts. But no; it turns out that the bolts are self-tapping! I wish it hadn’t taken me a month to figure that out; all it took was a Google search.
The rear seats are beige, and my front ones are blue, but oh well. They work fine.