When I bought my donor pack the seller couldn't find the the V5, I wasn't too fussed.
Now I'm nearing finishing it I think a age related plate would be better than a Q and give the option of putting a private reg on etc which is better for resale.

I have the chassis number plate that was cut out of the car and the engine number and possibly the reg, could I apply for a V5, not sure if the old owner send off the V5 marking it as scrapped? Any other ideas?

https://www.gov.uk/vehicle-registration-certificate-v5c-log-book
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/360103/V62_220714.pdf

See if it comes up on here

https://www.vehicleenquiry.service.gov.uk/

If it comes up then it might just mean the V5 was lost in which case apply for a new one