I have used the godzilla blow off valve before but I wasn't making near the power you are going to make. IMO the godzilla is a nice piece, marketed to people who do no need such a big bov. However, in your situation it would be perfect. It really is not that expensive last time I looked, not to mention you could pick it up from someone who realized it is way too large for their combo. Never used any wastegates that large, but I knew a guy running two tial wg's and it worked well.
68 Barracuda 440