This is a great website, but sometimes it takes time for someone to see your question and take the time to answer it. I'm no expert on '73-'74s, but I did a search and stole this from a dogger315 thread:
"If you want a race bike, I would go with the repro plastic. It is cast in color and easily replaced if damaged.
If you want your Elsinore to look original, I would definitely try to repaint your stock plastic especially if it is
in good shape like you described.
You will need to sand the surfaces for prep and to reduce or eliminate scratches then use a fill primer
to finish the job. The correct silver paint is available from
http://www.vmxracing.comAfter you lay down the silver, I recommend a couple of coats of clear for protection.
Of course the tricky part to painting flexible plastic is paint cracking. That's why it is a good
idea to include a flex additive to the paint.
If I was doing it and wanted to keep cost as low as possible while still doing the job right, I would get
a rattle can of the correct paint (since I don't know the code) and take it to an automobile paint supplier
(like PPG) and have them color match it and mix up a quart for me. While at the supplier, tell them what
you are painting and they can hook you up with the flex additive (same stuff used on plastic auto body parts),
primer and clear. Buy a reusable aerosol spray gun (aerosol sprayer with a detachable jar), follow the directions
and paint away.
If the plastic gets scratched while riding, you now have everything you need to refinish it.
Good luck with either way you decide to go."
Do a search here or try calling vmx.