Before and after...
This is one of my earlier auto-chops out of curiosity of what it might have looked like.
1953 Chevrolet pickup cab was added to original convertible, and rear side bodylines adjusted to create pickup bed. Only minor photo cleanup was done to remove cars in background. Original red version was also changed to black (and other grey and 2-tone versions not shown).

not bad, i like the rroof lines, but can you do cars with perspective or you just do side views?

Thanks Hugo, I've only began doing these auto-chops just for fun a couple months ago with the intent of side-by-side comparisons of models that perhaps should have been produced. My entry for the recent "C4 Corvette" contest here will be my first attempt at other than profiles.

This one's excellent. The proportions and the shape of the roof is just right! The only crit would be that the roof paint is slightly more towards magenta while the rest of the paint isn't.

Nice work!

Thanks ollite20. I'm still discovering the different ways to do color changing & matching and figuring out when each is appropriate. The pickup image used for the cab was also red but a different shade and for now I got as close as I know how within my photo editing program.

The roof is most likely from a clear day photo and the colder hue is atmospheric reflection of the sky while the base car was shot on a cloudy day.

What's the software you're using?
Here's a quick adjust I tried out. I added some colder hues onto the bright reflections on the paint by using the Gradient Map in Photoshop. I also blended some of the reflection from the hood onto the roof to match it slightly better into the image.

Thanks for pointing that out, ollite20. That's just something I'll have to practice more as it's not often used in my other standard photo editing. Y'all are giving me some high standards to achieve in order to meet with your own works as without better examples to match, one may never really strive for such improvement and I fully appreciate all critiques received.

I'm using Corel Paintshop Pro Photo because I can't afford the Adobe brands, but from what I can tell it's about 90% similar in capabilities. If digital editing was available yonder years ago, I may have gone to school for this type of work in my younger days vs self-training by experimentation for editing my own photos. This alteration was done just for fun at the time a couple months ago so I wasn't analyzing it quite to that extent back then as I was just mainly focusing on altering the car design out of curiosity.

Thanks for the altered example, I see what you mean about about the difference in sunny vs cloudy day shots and will watch closer for that when mixing images. I did try to find a somewhat close color of a pickup to use though for the cab. I'm not sure about liking all the blue-ish purple highlights on the body with the correction, but that can be personal taste with the amount of correction done in making it look more like it was taken on a sunny clear sky day vs cloudy day.

Here's two of the grey combo-versions which now I see needs the colored highlights included on the body somehow and I'll have to play around with that some more as I probably used the wrong process to make it grey in the first place.

Most evident on the gray version as it most notably looks desaturated. To some extent it does look like a glossy gray (instead of silver, which would need a lot more work to pull off).

And also, true, to make it a proper sunny weather there would need to be the specular reflection of the sun. The blue just by itself looks weird, I admit.