I know that Millen sold Chassis number 5 (also marked as #75 on the outside) 4 years ago or so. (I clipped the classified ad from Auto Week and put it into a frame.) That was a 3.0 liter twin turbo V6. I know that the last few years of IMSA they banned turbos and Nissan raced NA V8 under the same body shell.
Was this car at ZCon a 3 liter twin turbo V6? The motor sure does seem pushed back into the cabin! I do see what looks to be two turbos...