Changing out an older 340 motor to a newer fuel injected 318

Your truck should have two pumps, a low pressure pump in the tank and a high pressure pump outside. I'd think you would want a low pressure booster either in or out of the tank

There might be issues with the ECU and security, evidently in the keyswitch. Some of the hemi conversion guys should be more on this. That is, you might need to have the ECU diddled with which will cost some.

Might be issues with auto trans sensors, unless it was a stick