image from southtexasdiecast.com
Initially, I just did some sticker fabrication on the sides and back.
After looking at it, he said he wanted a wheel swap and a revised tempo at the side too. I agree, the plastic wheels, despite the red line, won't look as good as rubber wheels. So I got a donor, and swapped wheels for it and fabricated new side tempos for it. :-)
That looks better! The eyes are more visible, so from quite a number of angles the Joker's eyes look as if it is looking at you. Plus, the rubber wheels made it look a bit more menacing yet classy. And add a final touch...