Board Thread:Game Discussion/@comment-37524703-20190529101203/@comment-37524703-20190605134311

Confirmed: All 3's upgraded PORSCHE 919 HYBRID EVO cost 660 GC (and 3,254,700 R$), 150GC rewarded, net cost of 510 GC to complete Porsche 919 Hybrid Evo Championship

Last Engine upgrade will cost 1310 GC. In total it will cost 3265 GC (and 6,095,700 R$) to fully upgrade.. so you betcha that Exclusive series with 100 GC Reward is coming :)