Torsion bars - like coil springs - when put under load, take a 'set' - that is, they settle a little. Therefore, if the load is reversed, the ride height may alter by twice the amount of settlement. Provided a torsion bar is not overloaded, this settlement should only happen on the initial fitment, so I would suggest that if your bars are of uncertain handage - fit them, ride the bike carefully for about 50 miles, then check and reset the ride height of each bar. This will entail removing the pivot bolts from the rear links as the 2 bars may be fighting each other and not exerting equal loads on the swinging arm.
Regards,
Eddie.
