HI Eric, welcome!
I have a soft spot for Trans Ams as we had an '81 and my brother still has his '80 Turbo. Both in sorta not as common color combos. The '81 was white with the 5 color gold bird and full double pinstripe. WS6 handling package. Most white Trans Ams I've seen had either a red or blue bird. Got totaled but I still have the hood scoop. My brother's turbo is black with a 5 color red bird. Most black cars have the gold package.
Lets see pics of the '73!!!!!
I love the nose on the '70-'73 cars! On craigslist I saw a cool Frankenstein car with my favorite parts. Was a '79 with the smoked rear lights, T-tops but had a '70 nose and a '70 Formula Firebird hood! Was a 4 speed car too! Was only $3,000. Wish I could have gotten it.
What sort questions do you have so far about Cudas/Challengers?
In addition to what Chryco said, the 1970-1971 models are bit pricier than the 1972-1974 cars. Look at pics off the net, see what style you like first. If you are a numbers guy then opting for the "blank palate" base model car to modify may not be your cup of tea.
Have fun! Ask lots of questions!