Image Description: This Land Raider Terminus Ultra conversion was done in such as way as to use only two sponsons rather than the conventional four suggested by the Terminus Ultra Datasheet. This was the first major Mechanicus themed conversion that I did, I believe back in 2008. It inspired the Mechanicus themed Shadowsword and Stormblades I did shortly thereafter and eventually the entire Space Marine Spears Of Ares Chapter of which it is now a part.
The datasheet for the Terminus Ultra should answer all your questions and it is available as a free download on the GW website (http://www.games-workshop.com/MEDIA_CustomProductCatalog/m1180072_Space_Marines_Datasheet_-_Terminus_Ultra_Land_Raider.pdf).