R30 or r31 gearbox. the actual stumpy box is an r30 box. and the speedo output is on the left hand side of the box....and from my experience a 120y cable will not be long enough unless its routing it very direct which would not be the neatest

i ran a 200b cable and it was the right length to run down the chassis rail and then wrap under the gearbox to the sender

with my r31 gearbox (non stumpy) behind the CA i use a 120y cable as it doesnt have to cross to the opposite side of the car, assuming it is a right hand drive vehicle, and is therefore the correct length as it is from memory about 150mm longer than the 1200 one