New guy, From Kentucky

wELCOME.tough choices.I would (if I were buying my first car on a budget).i would look at the 70 dart as its running and so called rust free(many are rust free till you dig into them).The charger looks the roughest but still manageable.The 64 looks the cleanest but looks like some rust creeping in the quarter.If you want a classic and can keep up with the maintnanace the 64 will be unique.I personally wouldn't muscle up the 64 as I like the way they look stock.If you want muscle the 70 or charger will get you there with a nod to the 70 dart for being lighter.Tough choice good luck.BTW if I hadn't just bought a 72 cuda MoreDart's 71 dart would probably be in my garage right now,just saying.
oh and here is what the 64 could look like
http://www.forabodiesonly.com/mopar/showthread.php?t=173403