I've got the Hot Rod magazine issue with it in there, heres what the engine specs are:
Gen IV small-block with aluminum block and CNC-ported heads from the Cadillac CTS-VR program. The 4.110-inch bore and 4.00-inch stroke make 425ci. It uses a forged crank and rods, and pistons with stainless steel, barrel-type 1.2mm top rings, reverse-twist cast tapercut 1.5,, second rings, and 3mm standard-tension chrome oil rings. The compression ratio is 8.3:1 and a protptype hydraulic-roller cam tickles production lifters. Vlaves are 56mm on the intakes and 41mm on the exhausts, controlled with double springs, titanium retainers, and GMPP rocker arms. The damper is a production C5 Corvette part, as is the ignition ECU
Power: 1,070hp at 6,350rpm and 1,000 lb-ft at 4,750 rpm on C16 race fuel
Transaxle: Its a GM 4L60E four speed automatic overdriver mated to C5 Corvette transaxle.