Looking at the picture of the yellow one I would say they were 19's with a -60mm drop, but what you have to think is if your arches are bigger then you can fit a wheel larger than 8" or with a decreased offset.
This would clear the problem front suspension mount which prevents 8 1/2" with a 45mm offset. I reckon you could possibly go for 20's with an 8-8 1/2" width, you would need to run a 235/30-20 tyre with a probable offset of 35mm that 10mm would bring you out to the edge of the arch and clear the suspension. The rears would be easier just run a 20x9" with a 255/25-20 with a 35mm offset. (If you can find them anywhere)
This is all guess work and you would be better to find somone willing to experiment with it for you.