Additionally, the Vortec 5.3L engine uses a different electronic control system than the 350 Oldsmobile engine. This means that the Vortec 5.3L engine will not be able to communicate with the 350 Oldsmobile transmission's electronic control module. As a result, the transmission will not be able to shift properly and the engine will not run correctly.
For these reasons, it is not possible to install a 1999 Vortec 5.3L engine into a vehicle with a 350 Oldsmobile transmission.