1960s Difference between Fisher body manual and shop manual.('67 DeVille)

[Rhodes]

Can those with experience explain what different tasks these two manuals accomplish and why I might need both?

I don't mind buying both as long as they have a purpose. Thank you very much.

[Julien Abrahams]

I have both (from '54, '66 en '67) so I have an idea of the difference. The main difference is that the shop manual mainly focusses on things like engine, transmission, electrical system, brakes, suspension, all specific for Cadillac. The body by Fisher manual focusses on the body and is more general (next to Cadillac models, all GM body styles are covered). This manual focusses on subjects that are related to the body. For example, doors, window regulators, bootlid or the convertible top mechanism.
Hope this gives some insight.  I could send you a digital copy of the content pages from both, perhapse that helps as well.

[Clewisiii]

Also someone can explain how these manuals merged over the years.

For 61 it was all in one manual. Other then the line Assembly Manual which is basically worthless.

[Jeff Rosansky CLC #28373]

Also someone can explain how these manuals merged over the years.

If you think that's bad....
There is no 55 manual. You buy the 54, and there is just a thin 55 supplement.