[*13*]

Aluminum=Probably isn't going to happen in your budget. #1, in order to sell the aluminum car for a decent sum it will almost certainly need to look period correct. That will cost you...
Engine=If you build a BigBlock Car, Big Block is most likely going to be the key element in the ending value of the car. You can certainly build a small block to exceed the performance of many 427SO cars but, big money almost always wants the bragging rights.
Car=With your budget you can get closer to your 30k number & still be period correct with a small block car. Not to mention, the 289 cars have a lot of great history & number of great looks through the evolution of the car. Some of us have come to prefer the look & heritage of the Small Block Cobra.
I'd look up "Mr Bruce" here on the site. He does some pretty nice looking work from what I've seen & will probably pretty much get you to the point where you feel comfortable taking over.