The Khurasan Miniatures blog has posted photos of the 3D sculpts for some of the options that will be available for their 15mm Atlas Armoured Tractor.
From their website:
The Atlas Armoured Prime Mover will have many options to allow gamers to use this beast as they prefer. First up, the guntruck option, seen above, a rear box that drop fits onto the tractor to make it a one piece patrol truck, and a powerful escort for convoys of softskins.
That photo also introduces the pulse cannon fighting station, which is shown to the rear of the guntruck. This rotates like any turret, and will be sprued up with the rotary cannon turret, and a sprue of both turrets will be included for each weapons station, allowing you to use either one. Of course, you might prefer to have only one turret, rather than two, but closing off the hole should be an easy matter.