You have a grand ambition - but you have much research to do and much learning to undertake before you can build a bass. It appears from your profile that you already have experience with uprights.
Unfortunately, there is not much you will learn about uprights from working on electrics, especially solid body electrics. The two are completely different instruments with completely different types of construction.
To learn more about electrics, I recommend that you do the online research to find the answer to your question yourself instead of asking those on TB to provide answers. The first step I would recommend is to go to Amazon.com and buy Dan Erlewine's book on Guitar Repair, which is the bible of the guitar repair hobby. READ it carefully and you will start to get a sense of what's going on.
The older version of his Guitar Player Repair Guide is here:
http://www.amazon.com/Guitar-Player-...9961078&sr=8-3
The updated version is here:
http://www.amazon.com/Guitar-Player-...9961078&sr=8-1
In terms of upright basses, I suggest you open a Google search and type in "building upright basses" and similar variations. You will get hits. I did find one hit that offers plans for an upright - the plans cost $175, but that would probably be well worth it, because an upright will not be cheap to build.