72 was a good year to have
Since you are open to suggestions due to not having a drive train already, then you should think about putting an olds 455 in it. Most chevy guys think oldsmobile engines are not valuable so buying one cheap should be easier than finding a powerful chevy engine inexpensively. Next, the car would be worth a bunch more when you get board with the car and decide to sell it with the olds engine in it. The 455 olds makes gobs of torque in stock form and are very reliable if you do not over rev them. However, if the car frame is chopped up, without stock interior or has a cage in it or something to that extent, then whatever chevy engine you can afford would be the way to go. As for 383 or 400? Why not 582"? More is better for cheap power.
Bruce