There have been plenty of discussions on these topics, mostly within the Spider and GTV forums. Do a search. The short answers are that there is no simple way to "drop in" a '74 booster in a '69 GTV. You would need to convert the car to use hanging pedals. This is possible but not what I'd call simple. As to running the system without boosters, this is possible and has been done. Do a search for the details.
Best,