As much as I like my SA 1911 RO 45ACP it's not the one I'd take.
My keeper would be the Glock 23 40 S&W, with the conversion barrels for 9mm & 357SIG.
As Grifter said, parts are all over the place. I would also have some versatility on ammo.
Let's face each of us can have a love affair with a certain caliber cartridge, but the one you
will find most anyplace is a 9mm. That is the deciding factor on what size you will select.
Then it boils down to the make and model. Mine is Glock.
Now if there was any way to sneak another it would be my SA 1911.
OOOOOhhhhh, sneak a third my 300 BO and a 4th would be the
Ruger Mark IV as 22LR will be easy to find too.
Now I would be weeping cause the 44mags, 45LC/410 and 454 and others are left behind.