Has anyone ever seen PR adjusters with offset balls? Triumph 650 speed equipment from the dark ages (by Webco?).
The thread is stock, the ball diameter stock, but installed with the ball closer to the shaft. This effectively shortens the pushrod-side lever, and increases the rocker ratio. Downside: the ball must rotate a full turn during lash to work.

Could this be done with stovebolt adjusters? But for safety I would greatly increase the ball diameter (yes, new pushrods) so that the shared material is at least as large as stock.
Increase the 3/8" ball to 5/8" (a 5/8" ball bearing? Very hard, exactly round, cheap), with the outer edge of the ball in stock position, offsets the center by 1/8". The new ratio looks like 1.625:1, or +10%. Makes that .400" lift .440".