Hook, only way to do that with GV is to use a 3rd party app to tweak it. GV stopped using a single number for dialing out with in one of the recent updates. To the OP, if you want to go that route, there are tons of threads on here of people wanting GV to be free again.
However, I do believe the calls will still show up in the phone log, not sure of a way around that requirement.