s6 to V-8 do I need to change torsion bars

IMO the "float" problem that some are reporting can be ameliorated by a good set of HD gas shocks. Raising the spring rate at one end of the car upsets the balance that Ma Mopar put into it. So does upping the engine weight. That can be countered by an aluminum intake on the 360 and moving the battery to the trunk.

Usually, increasing the engine weight promotes more understeer. Conversely, increasing the front spring rate should promote more oversteer. What happens when you put in a 360 and 1" TBs?? Who knows??

I can't speak for the 74 model, but the 73 /6 uses the same bar as the 318 w/o A/C. (source: 73 Dodge Parts Manual) That tends to validate the assertion that the weight difference between the 318 and 225 is not that much.