The block to look for is a "509" Casting and a 2 bolt. You could splay the center mains if you want for added strength. If you are going to stay with a 406ci and plan to keep the RPM's down around 6000.. (6200Max)
You should be fine with the 2-bolt. I would try to get at least a Cast Steel crankshaft and make sure to have it all balanced. If you want more RPM or Nitrous you should at least splay the main caps or get one of them new Dart SHP blocks. These are just my opinions. I have a 509 casting was a 2 bolt block now a splayed block and it is 422ci. It is all 4340 and Internally balanced and I run it up to 6800 or so.
Your luck may very though.. 8)