mt2 .18ss, it's gotta be... I'm converting my old MT as soon as I can. These trucks (HPI MTs in general) are just great, it has to be said, the 4wd, the stance, they are just great for jumping, and as durable as any out there, plus parts are cheap. The .18ss is a serious bashing engine, I can't wait to install mine, but I gotta get some aluminium bits and upgrade the drivetrain first, or it's just gonna tear it to pieces.
On the subject of durability, I have to say that I have been bashing my truck for a year on and off, I'd say I only put about 2 gallons through it altogether, but I fly off the ramps, and roar it around all over the place, and the only thing that's farked is the body. I haven't HAD to replace ANYTHING. Now I just wanna go a bit faster and fly a bit higher.