JB weld, flex seal or full rebuild ?

The Herbert stuff looks really good on paper but they scare me. I went through THREE hydraulic flat tappets from them a few years ago and not one of them measured to the specs on the cam card. Not even close. Each one they took back, inspected and agreed with me. The third return, I asked for a refund. It was not a small difference, either.
Ouch X 3
Lesson learned the hard way.