Minimum engine weight first was mandated (at 95kg) in 2006, with the switch to 2.4L V-8s (the V-10s probably were at least 30kg heavier). Spec weight was 600kg, car & driver combined. 600 less 95 means the FIA were allowing 505kg for rolling chassis and driver.
Fast forward to 2014. 690kg spec weight with a power unit (nee: engine) spec weight of 145kg, which means 40kg
more is available for roller & driver than in 2006. If you guesstimate the weight of 2013's CURSE at 30kg, then 2014 still has an additional 28kg for roller and driver than on the previous season. Plus the 2014 wings and fuel cell are smaller and (some kilo or two?) lighter. Call it an even 30kg. That so many teams are complaining about a too low spec weight gives me to believe that either they are building some extraordinarily robust chassis, or everybody's engine, not just Ferrari's, shatters the 145kg barrier.
I think 145kg was a pipe dream.
You can see on
this chart how the minimum weight has changed over time. The cars have nearly doubled in weight since 1961.
I do not have a copy of the 2004 TR to know to a certainty, but I think the spec weight on the linked chart has an error. I think spec weight was changed in 2004 to 600kg, with 605kg allowed during qualies. The chart shows 595kg. But I cannot locate an "authoritative" answer, so I admit I might be mistaken.