Or not go flattening too soon Dave! Nevertheless, there is a way - in comes AI!! First let Object Selection make a selection of the car, hit Ctr/J and it’s on its own layer. Choose (right click) Duplicate Layer and save to new file. Now make a copy of the original combined file and ask Generative Fill to cover the whole thing with the background effect. It will probably make a job of it. Alternative might be to cut out the car area roughly and use Content Aware Fill. One of them should work well enough. Make the new background layer a Special Object then risk enlarging the canvas and Free Transform the background to fit. Drop the two together and it just leaves that back end of the car to sort. Might be worth a try?

From the Branson Farm and Auto Museum in November 2020. Done using the cutout, photocopy and plastic wrap filters in the filter gallery, the background is one I made for this. Multiple texture, overlay, brush layers, and adjustment layers. All elements are from my library, with no AI elements or tools used. I'll include the original jpg from 2020 also. Thought I'd share.

If you would like, please click on the picture, doing so will link you to the gallery page where the shot can be seen in higher resolution and full page. Thanks for viewing and Have A Blessed Day !!!