Found a video guide that helped with the reassembly, and man was doing the shoulders frustrating.
Anyway, have some photos:
First, the robot mode from the front. The paint turned out pretty well. I think the added details help the look, though of course I need to get new decals.
Now a shot with the windshield hatch lowered to expose the cockpit. The upholstery of the seats has been painted in gray to make it actually stand out.
I painted the mechanical detailing on the inner faces of the legs in metallic dark gray, so that it no longer goes to waste.
And to round things out, a shot of him in truck mode.
I will come back to this for further improvement when I get a couple of those liquid chrome pens to properly restore the chrome parts with, but for now I'm satisfied with the repainting.
With the painting done, the next step is to cast reproduction fists. And any other Ultra Magnus parts I can squeeze in when I make the mold with my Allumilite mini casting kit.