Is there no hope for finding the original part files? As you have discovered the STL files are close to useless. In essence, you have to rebuild the parts from scratch, using the STL files as an armature to build your parts around.
If you are lucky, the eDrawings were set up to allow you to measure the parts. That will at least allow you to check some of the dimensions.
I'm afraid the original parts are lost.
Can I actually build on my parts "on top" of the imported STL parts? u
What else did you mean by using them as an armature?
If you absolutely must have them fully editable I would do following.
1) Import the stl files one by one. Save them and give them a proper name.
2) Create a new part. Save it.
3) Create a assembly and put both parts in it.
4) Start to modell the new part and keep track of the accuracy by using the assembly as reference. Using transparency in the assembly will help yuu to find where the models differs.
OR if you do not need the full thread of history of all features....
Then I would just import the stls and save them as solidworks files. They will be "dead" but you can add and remove geometry to them. The assembly still has to be rebuilt any way as well the drawing.
Depending on need anz complexity, I would choose one of these options.
You might want to build your SolidWorks parts in the imported STL parts or you might want to build them as separate parts as Daniel suggests. I'm not sure which is the best method. In the past, using imported STEP or IGES models, I have used the "in part" method. It worked, but it's been so long ago that I don't remember if I had any problems that might have been made easier by using the "in assembly" method.
The STL part just gives you a reference to build your part around. "Armature" was probably not a good choice of words, as it implies that the STL part is supplying some sort of structure to the new part, which it most assuredly is not; it is only giving you a reference to compare to, probably just visual.