When it is assigned it's new number.(shinny new V5)
You need to tell your insurance. And get from the DVLA , an updated MOT and an updated Tax Disc.
I'd print this check list off!
I know the banks provide a 'letter of credit' for this type of thing that both parties sign and provides a level of security ref quality, delivery etc. i.e. compensation.
Probably a minimum spend though and you would need a sample first too in order to compare against the full order received.
I like the idea and probably would have a pair but would just prefer a nice 'Z' symbol would that not be better looking?
ONLY my opinion though no offense intended.