I use them for the "leman russ" tanks in my Guard army (I have two of them, "the hammer" and "the slammer").
They need a little work to
40k-ify, but not much, and it's easy enough to add sponsons if you want them (add them to the taller section at the rear.
Like this:
The turret and sponsons were scratchbuilt (I didn't have any actual sponsons at the time - since remedied).
Figures are
GW cadians with WF pith helmet heads for my NovaCastrian
IC (99th) Colonial Militia Regiment.
Guns are modular - I can swap them out for Battlecannon, demolisher cannon and punisher (shown) but I haven't built any others due to losing interest in
40k.)