5sp triumph box option, also involves going with a non standard, or triumph clutch

A 4 speed Manx gear cluster with a Commando first gear might work better. With a normal Manx gear cluster on a race track, the ratios are perfect everywhere except in a clutch start. The low first gear is needed to get the bike rolling from a stand-still. After that, first gear is never used. My Manx cluster cost $730 Australian. Most of the guys who race these days, probably use TTI gearboxes, so there might be a few Manx clusters about which are not being used. The gear spacing in the Triumph box might be wider. The Manx ratios behind the 850 motor are excellent.

John Maher is an old Victorian A grade rider. He races a 500cc Manx in historic races. When I discussed gearing with him, he told me that he has 3 first gears for his Manx which he uses on different circuits. Most of the gears from older 4-speed Norton gearboxes fit the Commando gearbox.