@Extreedoc If you can " prove" the build card they should/may register.
If it's a Landrover original card you may be able to check axles etc.
But to have got the Q it may have had all the axle numbers etc noted.
Now if you manage to find the chassis number Dvla may want an inspection & this will flag all engine gearbox mods.
Now I have never had a Q removed from a motor but I have proved build dates when released out the army & got earlier registration numbers.
To MOT a motor there must be a chassis number on it. Even if it stamped into a scrap piece of Ali.
Do not do this you could get done for "ringing" but Dvla won't stamp a new one if damaged or lost. Figure that out