I've still not been close enough to a Firestorm to check, but from photo's I've seen it looks like a simple job of flipping over the shift arm on the end of the selector shaft to achieve 'race shift' of 1 up 5 down.
Is this the case or will it need a bit more modification? It looks like the clutch slave cyl' might be in the way, if indeed it is the clutch slave?

Thanks in advance.
Ross.