if you already have the NCRS judging guide for your '73 you already have most of the info you need to prepare your car for judging but a good idea would also be to contack Roy Sinor from NCRS (you should be able to get his email off the NCRS website or from the Restorer magazine) and ask him to send you copies of the judging sheets.
The JG is great of course but where the JG may tell you that something "wrong" could be a 25% or a 50% deduction for that area it doesn't tell what the point amounts are to know howe many actual points are being deducted - the sheets are good for that information.
After going over your car very carefully following the JG and the sheets you will have a pretty good idea how your car should rate in judging. Now make a complete list of anything "wrong" and work off that to start making improvements.
Most people seem to feel the best method is one that equates to a points vs. $$ payback. for example you may gain 5 points if you change XXXX but it may cost you a LOT of money to make that change where another area that is incorrect may gain you the same 5 points but cost relatively a small amount. Look closely at your new list and start making the changes first that gain you the most points for the smallest amount of money and work up from there. Once you go thru and correct all the relatively inexpensive items rejudge your car yourself again and see where you stand. Does it seem like you should be in top-flight status yet/ If so than look carefully at your list and determine how much it's going to cost to make other improvements. Remember, top-flight is top-flight no matter if your points are in the upper or lower range to acheive that - it may not be necessary to spend that extra $1,500 (just as an example) to change out a wrong item if the rest of the car is good enough to top-flight.
I'd say one of the biggest things to go over on the car to make sure EVERYTHING works perfect - is your clock working, the ciggy lighter, all your interior lights, odometer and trip odometer, etc.
The NCRS website is a great place to gain info on judging and the process also besides the great people here on CAC. In fact, a lot of the same people on here I also see on the forum over there.
hope this helps a little