Jacques,
Your drawings look virtually identical to my parts. Since I sent you the private message, it has started raining again, so I will have to check & photograph tomorrow. In the meantime, this is two photos I took of my battery holder assembly when I first got it. The box frame has been very badly treated in past, so my knocking it flat won't harm it any further. The two securing bolts have already been removed, and are in quite good shape. Good enough to be reused, and would be acceptable starting point for taking patterns off, if you don't have suitable replacements.
What is the part shown in your first diagram? It doesn't look familiar to me. Is it to show location of the box frame in relation to the base plate?
The only thing I see missing from your drawings are the exact location of the three rivet holes where the two battery securing bolts attach the battery box sides. I can supply that information , once I get a good look at mine. Mind you, you can't get them too far away from where they need to be, if you go off your plans!
