The only Mod engine worth a crap (IMO) is the Cobra/Lightning supercharged engine. You can add 50+ lbs to the weight of a blown engine over one with a plastic Intake. That puts it close to 600lbs and probably over that because I don't think they include accessories in the engine weights. It's also bigger in size than a 429 Shotgun Hemi. Wheather that's impressive for a motor with just 390hp is debatable.