Some general information.
The 305 TBI engine is generally the LO3 engine. The 350 TBI is the LO5.
You can probably get away with using the same TBI but replacing the chip in the ECM with a LO5 chip so that the injection will be calibrated for the bigger engine. The TBI is more flexible than the TPI which injects X amount of fuel based on a preset fuel map. The TBI can still sense airflow sort of like a carb. If nobody else answers before too long, you can go to the autopart store or look up the required injectors online for each engine and see what they're rated at.
In addition to the chip you might need the bigger injectors as well, which would fit into the old TBI.
Double check me on this, but it's probably not as complicated as you want to make it.