First, the 400 transmission is a larger and heavier transmission than the 305 transmission. This can add weight to the front of the vehicle, which can affect handling and performance.
Second, the 400 transmission has a different gear ratio than the 305 transmission. This can affect the vehicle's acceleration and top speed.
Third, the 400 transmission may require different driveshaft and/or transmission mount than the 305 transmission.
Finally, the 400 transmission may not be compatible with the 305 motor's engine management system. This could require modifications to the engine management system or the transmission.
Overall, it is possible to use a 400 transmission on a 305 motor, but there are a few things to consider before doing so. If you are not confident in your ability to make the necessary modifications, it is best to consult with a qualified mechanic.
