Jeremy,
The 'radials' aren't really necessary if you mount the
antenna directly to the vehicle's body (metal car body is
the ground). The whole point of the antenna at the URL
is that he didn't want to drill any holes in his vehicle.
If that bothers you too, then follow the directions.
The rods you have will probably work as well as anything
else you can find. The difference in conductivity between
your rods and copper just isn't worth worrying about. The
difference in durability ~is~ worth worrying about!
Have fun...
'Doc