Rebel 300 0-60 7.85 seconds
Rebel 300 redline is 10,000 RPM (rev-limiter 10,900 RPM)
Rebel 300 top speed is 88 to 92 mph (reported by owners). Top speed is reached in 5th gear.
(Like many motorcycles, the Rebel 300 cannot reach full RPM in 6th gear.)

If I had Rebel 300, I would definitely add a tachometer. Because the engine sounds so revved-up, I think some owners shift up early, and do not utilize the higher rpm of the bike.
Also, I would keep the stock exhaust for a while and just drill one or two holes in it. After I went to a louder exhaust on my 500, I mostly stopped revving it up high.
Please see these pages:
Rebel 300 – Using its higher rpm capability | https://wp.me/PdeiSF-r0
Rebel 300 Shift points | https://wp.me/PdeiSF-v7