One of the programs on the
Beyond Binedit 3D Programs page here at MTM2.com is Anim8or. Based on its price (free) I checked it out a while back for the low poly GeneRally cars, however they didn't pan out and it sat dormant on my HD for some time. Recently, however, I gave it a second look.
The frame that is on both Gone Postal and Alter Ego is originated in Anim8or. In the program, you can create a box, specify it's length, width, height, and # of segments in each dimension, and then dynamically rotate the box with the mouse. It's the dynamic rotation that makes it so good for frames. If you are a more "spontaneous" editor that likes to play around with frame designs, it's perfect. And if you know what the basic length, width, and height dimensions of an MTM 2 frame are, you can build the entire thing in Anim8or. Then, convert it to mesh, export it as a Wavefront, and scale it to MTM2 specs in BinEdit.
...But wait, there's more! Anim8or allows you to extrude a line drawing, capping the ends to make a full 3D mesh. You can then click-and-drag all the individual vertices of the model to refine it, along with scaling and rotating vertex groups selected with a "lasso". It's actually somewhat amazing how powerful it is, and with the number of verts in most MTM2 truck accessories (engines, etc.), it's pretty much a perfect fit.
On ENM 2006, everything except the body, swaybars, and tires was originally made in Anim8or and then mapped in BE. It worked very well, especially for the engine, shocks, and axles. I would suggest that all editors take a look at Anim8or, it defies what is said about it on the "3D Programs" page - that being, "...it does not currently excell as a 3D modeler for use by MTM editors." In my opinion, it is a perfect tool for MTM2.