This is my calculation. Using 3.200 final drive ratio, in 5th gear, the engine produces 11,193 Newtons of force; 2,075 N rolling resistance; 9,118 N air resistance but @12,131 rpm; 170.24 m/s; 380.82 mph; 612.74 kph which is ridiculous. In 6th gear, the engine exerts 8,828 Newtons of force; 1,663 N rolling resistance; 7,165 N air resistance @8,482 rpm; 150.91 m/s; 337.58 mph; 543.17 kph, just about right since it redlines @8,500 rpm.

11,193 N = 2,075 N + 9,118 N @12,131 rpm 5th gear

8,828 N = 1,663 N + 7,165 N @ 8,482 rpm 6th gear

However, using ChironSS’ 3.364 final drive, in 5th gear, the engine produces 11,767 N of force; 2,186 N rolling resistance; 9,582 N air resistance but @13,073 rpm; 174.51 m/s; 390.37 mph; 628.11 kph which is not plausible. In 6th gear, the engine has 9,281 N of force; 1,742 N rolling resistance; 7,538 N air resistance but @9,146 rpm, which is still above the rev limit. However, since it has enough oomph but it’s gear limited, it can achieve a top speed of 321.82 mph; 143.87 m/s; 517.81 kph @8,500 rpm —redline. Whether it’s 337.58 mph or 321.82 mph depends on the final drive. We’ll see.

11,767 N = 2,186 N + 9,582 N @13,073 rpm 5th gear

9,281 N = 1,742 N + 7,538 N @9,146 rpm 6th gear

8,039 N = 1,527 N + 6,512 N @8,500 rpm 6th gear

https://www.linkpicture.com/view.php?img=LPic61d80e844e0f01522305364