Update
Summary - the painted interior passengers arrived yesterday!
With all the good advice above, I decided to be patient and wait for the 6-15312 and 6-29152 sets to come up for sale here or on auction sites. These are the 15” cars with painted interiors and figures. As the months rolled by I almost gave up and considered buying my second choice. But my patience was rewarded last week and I got all 6 cars in like new condition via auction site at a fair price.
They arrived yesterday and I put them on a length of track and powered them up to check lighting. WOW! Beautiful cars that are stunning behind those warbonnet F3s.
Great advice from you all, and I’m so glad I held out for these fantastic cars. Thank you!