We have a 406 filled that makes 702hp. You need to sonic test the block and look for thin spots in the cylinder walls and prepare yourself for things to move around. I think a better option would be one of the new SHP blocks. They may seem pricey but by the time you have all of the machine work for splayed caps and such you will be very close to what you can buy one for. JMO.
3.875 OR 4.00, small base circle cams, SJ rods, 3/8" rod bolts, stroker clearanced rods, lots of time grinding and fitting. It can be done but it is not easy. My 2 cents.
Curtis