Can a certain thing be printed programmatically on the vehicle?
For example, I want to write U1 OR U2 OR etc
On the roof of the vehicle programmatically
That’s a part of the vehicle’s livery, so not really. There are ways to achieve that (look into, say, this script), but it requires an insane amount of work on the vehicle side and is surely not for the newbies.
for number to be programmed it has to be its own mesh and material, the the script would have to trigger which texture to display. GTA does this by have different livery’s set as a unit, you can set a livery to populate which displays a unit number