Your choice should be based on what you want to do years from now, because one day you will wake up and realize any mistakes in choices you made a long time ago. Budget will be a huge part of it. If you want to build power over 750 hp I would highly recomend an aluminum block with a big bore. A 4.440 bore AL block should last a lifetime for most. Many rebuilds. In a duster at stock location you end up with a front / rear weight distribution good for nine sec ETs.
If you think you will want to go faster as time passes then a 540 to 560 cube aluminum shortblock makes a good base. I would go with heads similar to 440-1, since you can have pistons made that will work with many different heads allowing head upgrades down the road. A short dome for future compression increases, and valve notchs cut for the biggest valves and cam you will ever run. You can start with unported heads to help budget for the AL block which will set you back about $6800 ready to assemble. This all will give you a base to reach 900 hp at some point if you want. Time flys. I built my first nine second motor in 1998. I made two big mistakes. I sold a billet 4.5 crank, and didn't go with the AL block like I should have. Those choices eventually cost me a lot of money.