A Cyclone would be a good choice, somewhat under the radar at the moment and available with a big block.
These days, what do you do with it besides wax it?
That's pretty much how collector prices go,,,,, with one exception.71 Hemi Cuda, same rated HP as 70 and usually worth more at auction because of the one year only styling.If I was going to buy a muscle car it would be 1970 or earlier. Horsepower numbers dropped in '71 and it's my belief the earlier cars are more collectible. That's not saying there are no great cars 71 and later, just that they are less desirable to collectors.