need some help

Are you using the metal motor mount brackets, that bolt to the engine, from the 66 or a newer engine. You must use the 63-66 engine brackets and insulators (rubber). If I remember right the 74 used the throught bolt mounts, but the 67-72 or 73 used the biscuit. The 67-72 engine brackets will locate the engine too far to the rear in a 66-down car, if they will even fit the chassis at all. I have several 64-66 "A" bodies, and am working on a customers 72 "A" body, and just compared the brackets.