Similar to many other posters........I use an inexpensive clip on IWB postioned for cross draw and I make sure that it is not hindered by a cover garment or seatbelt.
My normal carry rig is a VMII and you would have to have ample time to undo a seatbelt, move a cover garment if worn, and reach back in a seated position and draw a full size 1911 from it. I've practiced that and I can do it, but I wouldn't want to have to do it in an emergency........thus the fast, effective, and confident crossdraw (but only in my vehicle).
A paddle rotating type holster from various makers would fit the bill quite nicely as well. Easy on and off and you can rotate the holster into a comfortable and efficient position. The reason I use an IWB is because if I don't want to take it off and switch the sidearm to my main carry rig, then I can just keep it in its general location or move it over into a better position, check the cover garment over top........run a quick errand out of the vehicle, use a rest stop, etc. and it remains secure and concealed without having a lot of fuss and attention getting.
Other options are good and available, but I like this one most for now. I have a very bad feeling whenever I secure my weapons in a location that is not on my person (console, door pocket, glovebox, under seat, etc). I figure the safest place in the world for them, is with me, on me. You never know what might happen.
Anyway......my .02