The problem is that you cannot install a car engine into an atv, bikes and atvs have transmission built-in the engine cases, thus they are small and compact, where as car engine's even considering a mehran engine has an external transmission making it bigger, and even if you can fit it in, it can not operate properly. So the basic thing is, you can't swap it with any car engine, my suggestion would be to get an engine from a good yamaha sports heavy bike, that'll do you good. Other than that, you can swap it with another atv engine, if you can find one.