At 120 kph, the unit range of km/kWh will drop drastically due to aerodynamic drag, and motor inefficiency, and friction etc. Even if it drops to 30 km/kWh, you are still at nominal:
96V * 3.5Ah * 30p * 30(km/kWh) / 1000 = 300 km range.
But you can't drive the whole way at that speed. Let's say you drive 1/3 at 20 kph, 1/3 at 60 kph, and 1/3 at 100 kph. The respective ranges are let's say 80, 65, 30 km/kWh for an average of 58 km/kWh.
So your range will be 585 km - still too high. I would suggest a range of 150 km, to make the pack as light and small as possible. So the p becomes:
150 * 1000 / (96 * 3.5 * 58) = 8 in parallel. Since the 3.5 is really a 3.3, and the 96 is really a 93.6, and in practice the 58 becomes a 50, and add a 10% margin, you need:
1.1 * 150km * 1000 / (26 * 3.6V * 3.3Ah * 50km/kWh) = 11 cells in parallel
I.e. two modules of 13s11p. You are down from 50 kg (110 lbs) to 17 kg. Much more manageable.
Note that the 150 km range includes high speed runs. If you were to travel 40 kph uniformly, your range will be about 225 km.