You guys are also forgetting just how crazy the variables in just the engine blocks can be. There was that article in Mopar Action (i think?) where they weighed about 20 different big blocks; early and late 383's, 400's and 440's. There were lowdecks so thick they weighed as much as 440's and all those supposedly 'thin-wall' late 440's weighed up to 20lbs more than some earlier ones. By this account you could theoretically find a really light 383 block that weighed 30lbs less than a really thick 440 block. All were standard bore i believe.

Then you have the rest. I've weighed the intakes, even they can vary through the years... bigger/smaller carb bores, open plenums, different bosses possibly.

I've weighed about half a dozen cranks, all steel, and the 383 cranks weigh NO less than the 440 cranks... again, all standard. I was kinda shocked at this. The cast ones are lighter though... you could lose/gain weight there, but i've never weighed a cast crank, so i cant say how much.

I'd think the piston differences would be negligible. The longer rods, pushrods, etc. would be a couple pounds tops.

Thermoquad vs Holley is a noticeable difference, different air-cleaners could be as well... if we're sticking with stock stuff for comparison.

You could theoretically find a 383 thats 50lbs under the 440, or one thats pretty much the same weight... especially with the typical Mopar stacked tolerances... but i'd wager that if you weighed 1000 stock 440's and another 1000 stock 383's you'd end up around 20-30lbs difference.