The only reason to take a Chevrolet 454 cubic inch engine block and turn it into a 468 cubic inch engine is for pure speed or to use it in a race car. How you build a 468 BB Chevy engine depends on your preferences. Have it done for you or do it yourself with the help of these instructions. Be prepared to do some work yourself and leave the rest for the professionals if this will be your first attempt at building a bigger big block Chevy engine from a stock block with factory bore.
Secure a factory 454 motor on an engine stand to build a 468 BB Chevy engine. Disassemble the stock 454 big block engine. Remove the intake manifold, valve covers and timing gear cover. Remove the rocker arms and push rods. Pull the heads off of the block and remove the lifters.