400 help

[Silverray76]

Hey guys so i found a 400 sb for sale its just the block, no internals. I plan to build it form the ground up and i would like some tips from a more experienced builder. I would like this motor to but out at least 475-550 or anywhere between that. The person who im buying it off of said it original and has never been resurfaced which means Im going to have the block resurfaced. Now Im going to go some kind of racing pistons also it there a specific bore size i have to go to? and would be great parts for the motor. Opinions would be helpful or recommendations.