I changed my US spec 4.08 differential to a 3.69 to cut down on the revs. The engine is still strong enough to pull away in second just fine (there seems to be some 'limited slip' when you pull away, allowing for extra revs and torque). When I floor it like Mike says, to engage first gear, it lasts for a very short time and engaging second can make the tires chirp. Not the kind of getaway that fits this car! So even with the 3.69 differential, I just pull away gently but strong in second.
When I returned from my first ever test drive in my current Pagoda, I asked the seller the same question: "so when does fourth gear ever kick in?".
I know some who installed a 3.27 differential, and a 'manual kick-down' switch in the console between the seats, for those occasions where the little extra oomph of first gear is helpful.
Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic