I have to buy a vq35de block.

I have see that people here sell forged block, but my question is,

Does the number in the motor match with the vin number on the car. If yes, do I have to register that the car has I new engine.

 

Ask your DMV office near you. Only they can tell you the real answer. One way or the other, that's going to complicate the title of the car.

 

what smooth said each place is going to have different rules. doubt it will matter though, never heard of anyplace who cared just keep receipts. only time it will matter is in the case something is reported stolen then they can use the vin to possibly find it, even cali dosnt care about swaps if it still passes emissions rules and they have some of the strictest rules.