HiCan I lock the gauge head of LC481/20 ML320?
What do you mean? Why would you like to lock the measuring sensor? Or do you mean whether you can the error with the M of the short?
If the short runs to seed in the mount, you can change the M. without problems. If the labeling of the scale is similar, then they’re also similar inside. You should also check whether the seals are ok. If you make something, change also noted wear parts. HH have them as yard goods, not expensive.