As promised, here's the tutorial on how I turned my Russ into a StuG-style Thunderer... If you want to make one yourself in exactly the same way, you will need a Chimera box as well as some bits from a Russ (namely, the upper body plate, the sponsons, and the parts for the hull lascannon), and as many track guards as you can get your hands on. Of course, feel free to alter it and use different parts- but be sure to post the results in the tread-heads thread, okay?
I've included some details on how my Panzer was built too, and for the record it uses just about all the same parts, only substitute the sponson bits for the whole turret assembly.
By the way, be sure to read the whole thing before starting, just in case you miss something important!
Okay, to start off, grab the wheel sprue. You'll need 6 of the small ones for the road wheels, as well as both the medium and large ones. Now, on the larger wheels you'll need to trim down the pin inside so that it is flat against the rim. The reason for this is that it helps it sit securely on the inner track panels.
Speaking of those panels, you should trim them down now so that there is a bit more space between them and the floor, and cut away the three raised bits marked below.