I've spent my whole life with cars as a hobby and a career. I'm 62 now. Yes, that accrued knowledge helps a lot but you can learn a lot through a bit of research if you are interested enough. For example, using the muscle car example, if you realize that the manufacturers produced different models of cars on the same chassis...eg GM "A body" cars or Chrysler "B Body" cars (look them up) then you will learn that a 1970 Chevelle SS is basically the same car as a 1970 GTO or Olds 442. The sheet metal and interior trim is different but mechanically they are all basically the same other than slight differences in engines. Same thing with Dodge Challenger and Plymouth Barracuda or a GTX and a Superbee. It is also easier sometimes to swap specs between mods made by the same author. Don't mess with anything to do with "graphic offsets" and carefully watch suspension component measurement specs between suspension.ini's and you are generally ok. Remember that you are doing this with a new car folder and experimenting....you really don't have anything to lose. Generally, all you need to do to swap an engine is to change out the engine.ini and the power.lut that goes with it. However, if you are changing a car from a small block to a big block you should really also adjust the car's weight and also usually it's CG (coefficient of gravity). CG is basically what percentage of weight is in the front of the car versus the back. Obviously a big block car will be heavier and also have a bit higher percentage of weight in the front of the car versus a small block car. The CG figure is found under suspensions.ini. If you have any questions feel free to send me a PM and I will be happy to answer any questions you may have. Have fun.... that's the name of the game.