Get a 427 kit from Coast HP. have a local machine shop bore the block .030 over to match the piston you purchased. (make sure the machine shop #'s the piston to the bores.) BTW it would be best if you started with a 70 -72 block. Dummy up a piston with no rings and start from the
oil pump end and swing the crank around by hand and watch the rod end for where it will hit. Take a die grinder and clearance the bottom of the sleeve and
oil pan rails where need be. The whole procees will take less than an hour. You will be surpriesd how little will need to be removed. Make sure you have about .060 clearance in all the spaces. Get it balanced! If you really want a 427 SB don't go for a huge cam! Don't spin it over 6000 rpm!
Stay with a dual plane manifold, get the best heads you can afford, a Holley 750 DP will work just fine. A good stock
oil pump is all you need, Tell Coast HP what heads you have and they will pick a piston for you, if you have alum.. heads 10.5/1 is okay, iron heads stay with 9.5 or less.
I have built these motors at home, and have had good luck with them, I really don't know why so many others put them down...
maybe it because they get their as*"* kicked so much.
Scott s