Overdrive or don't worry about it? !
2004R. I threw the coals to a few of them when I was into the Buick Turbo cars. But you need someone who knows how to make them last and it will cost a bit. TV Cable is no reason to not use the tranny IMO. Just part of the Hotrod life lol.... A guy on the board local to me (supertruck) put one in his Dart sport and would be a good ear to bend. Solid guy with good mechanical skill.
The GV is a killer piece and simplistic however from what I have read on here it a bit of a tussle to make it fit.
Either way you will want OD for Highway cruising.
JW