Thanks Jim,it looks like from the 2lb difference bewteen the 2 blocks that the 340 was lightened further than the 300 design,which I kinda thought happened anyway.Thats why Buick increased the main journal size,they used the bigger journal cranks to compensate for the lighter castings they used with the taller decks,just like they did with the 400/430/ 455 block's monster 3.25" main journals,to stabilize the harmonics that a smaller main journal cranks would emit with the thinner castings. Which doesn't seem to be an issue with a 300,but then again it has .450" less stroke than a 340,so? If a sbb 340 is made to have a finished wall thickness of .180",and the deck height difference between a 300 and a 340 is .645" then times that by 8 = 5.160" of extra cylinder wall of .180" thick and 3.75" in diameter,that alone should be over the 2 lbs difference between the 2 blocks. Then you subtract the main journal housing bore metal that is removed to house a 3" crank journal vs a 2.50" main journal. Bearing caps about .900" wide X 5 = 4.5" long X 3.188" diameter with a .250" wall thickness. These 2 would probably be close in weight to cancel each other out.Close anyway,BUT,then there is the .645" taller deck comes back into play with the metal surrounding the extra cylinder wall hieght that raises the deck times 2 for both sides should be quite a bit more than 2 lbs with a minimum thickness of .125" to around .188" to hold the coolant in. So weight was taken out in other areas to get the weight down closer to the 300's weight. Unless they just made the outer case thinner to get the weight down? In any case,you're probably right,but I can dream until its confirmed can't I?