The .3ds format seems to be well docmuneted here and here and it uses identifiers. Just remember that things are reversed so 0x4120 = 2041.
RT3's .3dp format is documented on WP&P's site here(down the page a bit)
I don't have alot of time (or brain capacity
) to figure all this out but but hopefully we can stir up enough discussion and get enough interest in this that we can understand how to create RT3 models using a 3D modeling program such as blender.