Sound proofing will help to reduce the vibration and insulate the sounds from the engine bay to the internal cabin via mainly the floors and doors.
Try the site sponsors that advertise their services here or just get a non-obligatory quote. Remember that there are several diff types of sound proof material out in the market but basically the concept is the same. The thicker the foam, better the vibration absorption and insulation, but more costly.
You can even buy the material from local or online shops and DIY via Youtube.
Whatever the case, from the outside, it will still sound like a taxi...