Help! Engine Vibration

What year is the 318??..some early ones especially truck motors came with forged cranks,but most 318 have cast cranks,if its a internally or externally balanced crank,you may have the wrong flex plate on it,or the wrong damper..just a tip for ya' ALWAYS balance a motor when you have them built,it save you the headaches your having now,i;m surprised the builder did'nt highly recommend this...