You will need different engine mounts I believe. And as for as living in Ca., since it is a 81, you can do it but when you are done you will have to take your truck to a referee to get checked for the engine swap. Further more, say you drop in a 2005 LS engine, then your truck will have to be smogged at 2005 levels, and from now on it will be checked at those levels. But you will get a sticker to put on your truck and along with your registration stating that you are approved to have a 2005 engine in a 81.