Clunking noise after getting new short block put in

I recently picked up my vehicle from Ford service center after having to get a short block put in (due to recall damage concerning the cooling system). They replaced the block, all one-time use parts/gaskets, the crankshaft pulley, and did a front end alignment. On the second day of driving I started hearing clunking noise coming from the front right side, it sounds like something slapping the underside of the car, it is not constant and doesn't always sound the same. I was thinking suspension but the car steers tight and smooth with no knocking, and rides smooth and straight with no vibrations, even when the noise appears. I checked for a loose wheel well, plastic trim, body panels and splash guards under the car and everything felt tight. The car runs smooth and engine sounds normal when cruising and accelerating. Any Ideas? Thanks.