If you want Torque Thust I would start with the biggest bolt pattern you can. 4 1/2 requires the lug nuts and spacers to be machined to reduce the diameter. Simply not enough clearance at 4 1/2" .
Though it can be doen as seen here. My American 200S were done the same way. 4 3/4 would help. 5" would be the best route. Headers were built by Ernie Miyomoto at Motofab. He does nice work. If this thing weighs anywhere close to mine it should be a runner. Best Machine dyno slip says 965. We'll see.
Doug