Two important questions need to be answered. Are you sticking with the stock block and what fuel do you plan on using. 10 to 1 compression is fine if your running E85. Stock block will only handle 600-700 rwhp reliably. Smallest turbo I would use would be a 76 with bigger exhaust housing. An 80-88mm would be a little more suited on a 408. Hey, but what do I know.....
Man, if only there was an awesome fully girdled stock block 10:1 (depending on heads) 410w that could handle 800+ hp for sale