Also commonly known as my "Abrams Russes", these are the conversions that I use for Leman Russes in my IG army. All told the conversion takes about 16 hours or so to finish per tank, but I think that the end product is worth it. I'm working on finishing the tutorial for how to build one of your own, and while there are a lot of steps its actually a rather easy build to make.
To make one you will need a rhino, a predator, and a landspeeder as well as a decent amount of plasticard. Not much putty work involved in this one, but you will still need some to fill in gaps in the final product.
The body only takes about 4 hours to make and the turret takes about 8 or so to have finished. Honestly it probably takes me less time to make one now that I've made five but it can vary, the demolisher took a lot longer given the extra work I put into the TUSK armor upgrade kit.
More pics of these guys after the weekend when I get to take some of them on a battlefield at FTW Games.