4D56 isnt much heavier than a 4D55. They are almost the same engine. When you go for a 4D56 try to get a turbo intercooler one. Dont worry about suspension, as it can handle it with ease. Nothing need to be done with brakes either, your not replacing it with a rocket engine. The 4D56 is a way better engine and it will also couple with the gear box with no issue. Im an engineer for Mitsubishi NZ so take my word.