[nxtruck]

It all depends on what you're trying to do. If you're looking to build a hot street/strip cruiser, then save some money and build a 406. You could probably get by with a factory crank, a set of ARP-bolted 5.7 rods, and some inexpensive forged pistons. If your power expectations don't exceed 450-500 or so, this setup would work for you.
If you're looking to make more power than this, then maybe a good aftermarket block with a 421-434 rotating assembly would be worth looking into. I can tell you this: I'm currently running a factory-block 434 and it took a lot of grinding and fitting to cram it all in there. And then I'm still up against the weakest link, which in my case is the block. I wouldn't build another 434 using a factory block.
Just my opinions...