[AmigaBlizzard]

After setting the virtual world of the player and vehicle, try to use PutPlayerInVehicle and then reposition the player (SetPlayerPos) to the coordinates he should be standing.

That's how you show vehicles in class selection as well.
Just setting them in a virtual world and interior 0 won't show them.
You need to put the player inside, then outside the vehicle again to make it appear.