Download this hex editor. Its tiny, simple, clean and I use it.
http://www.physics.ohio-state.edu/~prewett/hexedit/Open your SM file(remember that although there are many parts to the B17 you dont need to clone all the files... eg wheels etc stay the same.)
Goto
'find' and search (IN ASCII MODE) for
'Material' (Case Sensitive)
To keep things simple, in the right hand column just change all the
'B17's to
'C17' and if you wanted more copies use D, E etc. (you can insert characters but why bother when its easier to replace)
The materials are all bunched together so its not too hard to find them.
Then file save as
'C17_..etc..)
Then use the find/replace feature in notepad to change the rs files for your cloned model

done

The B17 is a big object to clone like this but using this technique is very simple for basic objects... and overall even for the B17 takes about the same amount of time as doing it in 3dmax.