Does anyone sell an assembly manual for a 68 Plymouth B Body? Thanks!

Do you have an FSM (factory service manual)?
Lots of body info in there as well as the mechanical & electrical.
Not aware of a factory assembly manual dedicated strictly to body like GM had in that era.
For GM cars, I used to buy the separate Chassis and Assembly manuals.

I think there's a pretty good book available for the 69s that gives step by step assembly procedures.

Do you happen to recall what that is?

The one I was thinking was 69 Road Runner in detail, but looks like it's more of a history book. Mopar B-Body Restoration 66-70 looks more like it. I may want a copy too!

There are three books, all are not 100%, all have some good info, and some questionable. Also ask questions here and get the books by mmcdetroit for a lot of good info on fasteners and volume 4 looks interesting.
The 3 books (again ferret the info and ask questions here) Paul Heard: Charger, Road Runner & Super Bee Restoration Guide, Paul Heard: Chrysler Muscle Car Parts Interchange Manual (mistakes), and Kevin Shaw & Mike Wilkins: Mopar B Body Restoration. I wish Badalson would publish some helpful info, If nothing else their parts catalog is interesting to review, and to get parts, some are $