did you miss the part that Webley valve sits in a plastic housing, where as the Crosman 2240 has a steel tube that the valve mounts in and the open boss valve can then be sealed with O-rings and pined by screws from the outside of that steel tube
why would anyone waste there time doing what you what, by remaking a 100 buck gun
and even when someone converts a 2240 to air you don't charge them up to 2000 to 3000 pounds, 1500 would be tops