Not much room at all. That HVAC box has killed me. Keeping A/C and a intercooler behind the stock grill has been a chore. From cutting the firewall back to all custom turbo piping.
I did get my air intake built the day I was at the house.
Maybe you already have or are aware but they offer a 1.15 turbine housing instead of the 1.32, Jacob at HTT hooked me up with one for my S480. He said they spool quite a bit better and work great with the twins, he said still seeing a 1000 hp out of them too.