All that I was eluding to as for hood clearance was the fact that several B-Bodies like yours were built with a big block from the factory and that a ''fairly'' stock 440 would not need as much performance work done to the inside of the engine as the 340 to equal the power output and drivability that you require.
A mild 440 with a dual plane intake that is roughly stock height should easily make 1 HP per cubic inch with headers, some mild port work, and 9 1/2 to 1 compression ratio , and you would have to breathe on a 340 quite a bit more in comparison to make that level of power and the 440 would have gobs of torque compared to the 340 at this level.
You could sell the 340 to someone for a pretty good sum to offset the costs.
Now all of my suggestions go out the window if you REALLY want to keep the 340 in the car...
Beautiful car by the way!
