TH350
IF the TH350 has a Chevy bolt pattern and has the short tail shaft, then it is the same length as a powerglide and will bolt right up. But some TH350's do come with an intermediate tail shaft or a long tail shaft, not to mention having a Pontiac/Olds/Buick bolt pattern case.
Make sure that the flexplate has the extra bolt holes to match the lugs on the TH350 torque converter. Sometimes the flexplate has only the one set of holes and needs to have the other ones drilled to match the converter.
Bill Mitchell