Stop in for a cup of coffee
The ports on the LD340 are taller to match the intake ports on the 340 (and up) cylinder heads.
Also, the runners from the upper and lower planes go to different intake ports, they are swapped. I have no idea if that makes any difference, I would guess not. Unless that change made it possible to make the runners a little longer.
And the plenum is larger on the 340.