I really think the 3.55s would be perfect for you.as i said my gn has almost no torque(compaired to a 440) without the turbo spooled up and on the highway it has more than enough power to over come hills without kicking down.But remember when cruising it takes no time at all to get it spooled.I would run a 2800-3200 converter and use lockup.And from what i have been told on turbobuick.com the turbo cars like a fat powerband that the 3.42-3.55 give you.