I have owned a 1958 Chevy Belair about 2 months. 350/400 Turbo TB Fuel Inj. I stepped into it real hard (yeah, I know) and this horrible sound came from under driver side. Long story shorter -took it in, was told tranny mount, $$$ it actually was, I saw the broken one. This solved the thumping from underneath but the car still has a horrible crunching/grinding like sound with loss of torque upon acceleration, from what seems like right from under driver’s seat. Engines runs strong/tranny shifts good. I have been all over and NO ONE has a clue or has offered the stupidest suggestions. Anyone?