I am so confused HJ Sandman

[RodneyHZ253]

Thanks for the reminder Rodney. According to this engineering document the retainer changed in Aug 76. I like how the XX7 & XU3 seems to be an afterthought at the top of the line.
Retainer Headlining.jpg

What a great document bit hard to read but it looks like it also gives a reason for the change to make installation of ceiling easier