1979 Chevy Camaro Quick response on throttle sluggish take-

So I just recently rebuilt my small block 350 and had it bored 30 over, the engine runs beautifuly and 100% better then before anything was done. My problem is that even thoe the engines response to the gas is great the car itself feels like its being held back MAJORLY almost like the brakes were stuck but there not. Basicaly the car moved quicker when the old engine was in it... Can you help>??