I cannot check the Challengers, as I haven't collected them yet. But a google search indicates that they are do indeed require flat seated bolts. Thanks for the heads-up. 
I have just measured the bolts that I was using previously for my other set of 17"s, and I am relieved to say that they are all 45mm. The McGard locking wheel nuts are too! Phew!
Edit: While my previous bolts were 45mm, they were not flat seated.

I have just measured the bolts that I was using previously for my other set of 17"s, and I am relieved to say that they are all 45mm. The McGard locking wheel nuts are too! Phew!

Edit: While my previous bolts were 45mm, they were not flat seated.