Lexus warns that the torque converter-to-flexplate bolts should be replaced any time a torque converter is removed from one of its vehicles for service.
The carmaker points out that there are several different sized converter bolts depending on the application.
Furthermore, some vehicles use washers underneath the bolts; others do not. Failure to use the correct bolts and/or washers can cause subsequent damage to the torque converter.
The accompanying illustration shows how the converter bolts should sit when either a correct and incorrect bolt is tightened. Notice that the bolt should sit flush and never bottom out on the flexplate. If it does, you've got the wrong bolt for the application.