I've got a dead 2002 M62 engined L322 ready to remove saleable stuff from before scrapping.

Any thoughts on dismantling a prins sequential system with half full toroidal tank in boot? "Gloria" 2002 L322 Voguish V8 LPG - carcass
"Jessica" 1996 Disco 1 300 TDi Auto
"Harriet" 1994 Disco 1 300 TDi Manual - Gone
"Daisy" 1992 Disco 1 200 TDi Manual - Gone

the tank should have a non return valve fitted so once you bleed the lines from tank to vapouriser (obviously in fresh air away from source of ignition, drains etc) then you can remove the tank with the lpg contained, you'll need to be careful where and how you store the tank prior to disposing of it, there is a PRV that will vent if the gas expands too much in the tank so keep it out of this lovely sun we are having!

Unless you’re planning on fitting it to another car yourself it’s probably not worth your time to remove it. Anyone with the skills and gear to fit, calibrate and certify it isn’t likely to bother using secondhand bits.