Has anyone else done something like this? We did it just . . . well, because . . .
It was a light but very fun project, particularly since my wife really got into it and helped me with a lot of the decision on what goes where.
We updated my downtown area traffic, etc., by about twelve years, from "1956" to "1968."
So we went from this . . .
and this . . .
To this . . .
And this . . . . (yeah, I know, the cop car is from even later, but . . .
I all started because of Adam-12. When I put the completed car on the layout a week or so ago, my wife pointed out the car was way out of the 1956 time period I had for all the other cars on the layout.
Anyway, some things changed a lot from '56 to '68. for one thing, there are many more Volkswagens now. They seem to multiply like Rabbits (Oh, wait! That model is yet another decade or two in the future, isn't it?) 
And the Ford dealership went from being a dowdy to being waaaaay cool!
Yet some things changed but stayed the same. When Veranda Turbine shows up at Dean Martin's club to see Dino and the Duke, she is still driving Italian style and coachwork driven by Chrysler hemi power (Dodge C. B. Thomas Coupe, Dual Ghia)
She's a busy girl, too, for she is just down the street, too, where she has traded her powder-puff Chrysler for a rocket of a 390 T-bird.
Lord Peter Whimsey stayed with a theme that always worked for him: shiny black paint, styling to die for, twelve cylinders, and if you have to ask what it costs . . . . (Daimler Double-Six/Ferrari 275 GTB)
But there were big changes, too. Nick and Nora Charles couldn't find a Packardthey liked n the mid '60s, largely because they couldn't find a Packard. But this Impala SS 427 caught Nick's eye. Asta rides in back and has learned to operate the power windows with just one paw. Nick Jr. is now 16 and not allowed to drive this, at least not that Dad knows.
Joe Friday and Ben liked their unmarked Ford sedan, but the Department decreed its all Chrysler sheet metal now, so they have a new unmarked car - they don't complain too much 'cause it has AC now.
My made up bad boy detective, Trayne Rekk, still drives a sporty convertible when he's off duty, and still has his babes with him.
And my favorite vignette on the layout. These guys have been there as long as I've had a downtown, long before all the detectives. Two buddies just out of school and still single, meeting on Saturday mornings downtown to share what was, in 1956, an uncommon passion for sports cars. Twelve years later, they are married and fathers, in need of a back seat, and without time to spend half the weekend fussing with S.U. carburators and Lucas fuel pumps . . . but still cars guys through and through . . .
