So I had the Testarossa on 26/28 upgrades, and have just thrown the last two upgrades on it for the exclusive series.

Rewards are as follows for those interested:

25%: R$10,000 and 5GC
50%: R$ 20,000 and 10GC
75%: R$ 20,000 and 10GC ( yep, same as 50%..)
100%: R$50,000 and 25GC

Total R$100,000 and 50GC

Somehow I don't see myself throwing 2075 GC at the LaFerrari to upgrade it for the exclusive series as I've only got it at 12/31...