Tiberian Sun/Warhammer 40K conversion

[Asmusei -Faceless Hunter-]

I wouldn't blame any of you for not knowing the game Tiberian Sun, but I used to play it almost obsessively. Now that I'm into 40K and have some modeling experience, I'm thinking of building some of the units from the game to scale.
For example, the Titan is the main battle tank for one side. It has a 120mm inner-bore cannon, equivalent to the same size as the Basilisk's main gun.
I'd also like to build the MK.II Mammoth from the game. This one has two Rail Guns on each side, along with two SAMs on top for AA. There is a cut-scene depicting a single .50 Cal mounted under the front, but I won't use that as it wasn't in-game.
It'll take quite some time to finish these guys, but I already have high-dense foam, the pink stuff used in construction, so I should be able to build the main bulk easily. Any suggestions? This'll be a first-time for me, so if you guys have anything to recommend...  

[Hoxtalicious]

Ah, Tib Sun, how I fondly remember waiting for that game to ever release some day. I also remember that it had massive maps and really, really slow units.  

[Asmusei -Faceless Hunter-]

Yeah, kind of like Apocalypse.