It should be a top oiler with 4 bolt mains. C3AE-6015-AB is the part number.
Here is a pic of a broken one with the HP markings http://www.mustangtek.com/block/C3AE-6015-AB.html
list of blocks https://www.fordification.com/tech/castingnumbers-FEblock.htm
63 R Code - specific parts http://427galaxieregistry.com/1963modelyear.html
There is no C8AE with a AB listed - The C8AE-A is a 427 side oiler. The photo on the Hemmings page looks to be the right engine block. Someone could figure out from the casting date if it's right for the car. There was probably a longer time from casting to installation of these engines since so few were sold.
Here is a pic of a broken one with the HP markings http://www.mustangtek.com/block/C3AE-6015-AB.html
list of blocks https://www.fordification.com/tech/castingnumbers-FEblock.htm
63 R Code - specific parts http://427galaxieregistry.com/1963modelyear.html
There is no C8AE with a AB listed - The C8AE-A is a 427 side oiler. The photo on the Hemmings page looks to be the right engine block. Someone could figure out from the casting date if it's right for the car. There was probably a longer time from casting to installation of these engines since so few were sold.