I am chopping the same base at the moment, As I am not very good at reflections either I have used the car in the new background for how the reflections will look. There are some people on here though who can do reflections from scratch.
Overall on your chop, parts of the brush are looking good, like the rear bumper. Though I think would look better without the bright spots. Might also be worth changing the rims as it obviously front and back are from the same donor.