Timing belt causes severe engine vibration

I have a 1984 Chrysler Lebaron, 2.2, 4cyl, turbo 175, ooo mi that I bought new. Car has had the best of care, and has always been a great ride. Recently, had a noise under the hood that sounded like fan belt rattle, mechanic said timing belt and replaced it, replaced the starter and valve cover gasket.I got the car back with a severe engine vibration, went back and fourth to the mechanic because, my car was tareing itself apart with the shaking, and it did !A broken motor mount, two broken turbo lines, three vacuum leaks, but the vibration wasn't fixed. All through this, they are saying that the "Timing Belt JOb had nothing to do with the vibration. They put some high tech engine cleaner through the car, told me to drive it for a few more days. It was vibrating so bad, that two days later I started for their shop, and the head gasket blew. So, now thats been sent off tp repair, and they now are saying, thats what the problem was. You have to know that the original work on my car was done in Feburary, so I'm still thinking the timing belt was the cause. The car has always run smooth, started easy and had a lot of pep even for an oldie. This whole thing has reall got me upset. Would really appreciate your input. Thanks