318 vs 360 weight

I think V8 torsion bars should be the same, you will be fine, but it would be a good time to upgrade if you want a bit of a stiffer ride/ handling. And also a thinner torsion bar has to be twisted more to keep a heavier front end at the same ride height, I think this also helps in weight transfer in drag racing as well. But it is also hard on the bar in everyday driving.