When should you upgrade torsion bars?

I have Mancini XHD leafsprings, U.S. Car Tool subframe connectors and PST 1.03 torsion bars on my 1970 340 Dart and it handles great, compared to stock 1970 it handles like a formula1 car! So in other words replace your t-bars with 1.03 bars even if the old ones are not wore out, You will be happy

Jeff