M30-31 pickup cab questions

[Vin-tin]

Using my pictures as reference, i'm hoping someone can answer my questions about my truck (M30-31 soft top/non-indented firewall).

#1) How does the seat back fasten? I've circled (in red) the parts "I think" is what fastens it. The 4 clips spot welded onto the cab back and the 2 clips (one is missing) screwed onto 2 wooden slats. Is this correct?

#2) What is used for the lower door bumper? A rubber bumper goes into the hole in that triangular cab brace. (circled in green) None are listed for that purpose in the catalog. I've narrowed it down to a few choices but none are for pickups.

#3) What are those raised oval areas for on the seat riser? (circled in blue).
Are they necessary?