Illinois has a cool website now www.cyberdriveillinois where u can actually see if a plate is available and even order it. Could change plates, but its like $78 just to change and then u still have to pay the annual fee again.
It could stand for:
1: first son born
5: fifth day of
4: fourth month
or some relation to car 54 where are you from the oldy tv or movie, not sure.
or could be 154 hp which would be a 50% hp upgrade.
Lets see, I'm in Illinois, and your in Texas? If you were closer, I would be happy to help you out. Your buy the few supplies and I would supply the 1 hr of labor. I bet I could have yours shining in 1 hr, yes 1 hr. Got any pics of your engine or of your car. I don't think I have seen them.