289 With C-4 Swap Or What?

WHOULD IT BE EASIER TO SWAP MY 289 FOR A 351W AND SWITCH TO A C-6 TRANSMISSION?OR JUST REBUILTED MY 289 AND KEEP THE C-4 ? I NEED HELP!!!!??!!!!??!!! I wanna get my stang in the low 12's would a new Edelbrock Performer Manifold and cam kit plus a Edelbrock 600cfm carburetor w/ electric choke get me there? i already have full length headers and exhaust!