Just a side note on the Master Parts catalogs. They almost all have a "Common hardware" section that lists hardware by type, ie; screw, machine etc. and under each category they will list the primary dimensions like 8-32x3/4" or such often along with a picture to detail a specific style or design feature to help in identification. Each of those has a GM# that coincides with the majority of the hardware listed in the Master Parts Sections like cab, etc.
Yes, it can be very time consuming and tedious, but if you really need to get down to the itty-bitty level, you can search through and find help in figuring out what you have or need there.
I'll 2nd Kevin's note about asking folks for help.

Some can remember off the top of their heads where this or that widget or thingy goes. We even have a special
Name that part... forum to ask such questions.
