vibration issue

The crank pilot (front nose) sizes are as follows.
TF904 to 1967: 1.550"
TF904 1968 on: 1.810"
TF727 1962 on: 1.810"
If the TA 340 came with a standard transmission though, I don't have the size of the crank hole. I know when I worked at a GM dealer back in the day, the crankshaft for a standard was different than an automatic. Perhaps someone on the board who has a standard transmission in his car can give you the size of that hole in the crank.
Also, a 1969-1973 340 had a cast crank, so the converter will have two small weights on it(flywheel side of the converter) that measure .875" x .625" x 1.80".
The attached PDF shows you (rear of crank) the difference between a cast and a steel crank.
Hope this helps.