I'd suggest the MGT chassis - it is made from a single piece of extruded aluminium and, from what i have read is much stronger than either the Savage or LST chassis, both of which are made of several interconnected parts.

With the plastic mudguards installed you also get a lot of space "up top" to mount everything - electronics, engine, tranny fuel tanks (there is even enough room for a second fuel tank with very little modification)

The picture is of the aftermarket machined chassis - the stock piece has less millings.