you will need a manufactres reciept

i.e ford

as ford no longer sell these shells anymore then it will go on a q plate unless the shell has the original reciept

from dvla website

In order to retain the original registration mark:

cars and car-derived vans must use:
The original unmodified chassis or unaltered bodyshell (i.e. body and chassis as one unit - monocoque); or a new chassis or monocoque bodyshell of the same specification as the original supported by evidence from the dealer or manufacturer (e.g. receipt).

And two other major components from the original vehicle – ie suspension (front & back); steering assembly; axles (both); transmission or engine.

If a second-hand chassis or monocoque bodyshell is used, the vehicle must pass a an enhanced single vehicle approval (ESVA) or single vehicle approval (SVA) test after which a "Q" prefix registration number will be allocated.