OK - transmission and 'cooling system and fluids' are the only parts of that that aren't already counted in the engine, and with cooling system and fluids that'

OK - transmission and 'cooling system and fluids' are the only parts of that that aren't already counted in the engine, and with cooling system and fluids that's already being generous. So we're talking an engine that doesn't need a transmission and runs cool. Hmmm. Transmission often counts the differential, without which you can't very well turn corners. You're going to need a reverse gear at minimum and a big part of the point of a transmission is to let you keep the engine in an optimally efficient rev range, so I suspect it'll still gain one. No radiator? Possible, but to productionise it it'll have to be able to run in both Siberian and Saharan conditions. They're both a regular part of manufacturer sign-off tests for road cars, that it can handle extreme cold with lots of short runs to stop it warming up properly and extreme heat with lots of long runs and soak tests to stop it cooling properly. Personally, I'd expect it'll gain a cooling system. So, even if the gearbox, diff, radiator and all associated fluids weighed 1,000lbs (unlikely I think), I don't think they could gain their weight quota because I doubt they can really eliminate them.