When installing a Torq converter other than clicking it into the transmission 2 or 3 clicks to fully seat it, is there any other items to check? My engine builder is leaning towards a torq converter malfunction or it pushing the crank causing bearing failure. only think I know is that when I mated the engine to the transmission it was smooth and needed no forcing what so ever. The torq converter was new purchased from Branting, I even had it cut open by them to inspect and all is good. All the bearings, crank are shot. Although he does admit that I shouldn't have gone 3K+ mile if it was installed correctly.
Its a 75 block with a 96 4R70W transmission.

Do you have the spacer plate in between the engine and trans? If the plate is missing it might put to much pressure on the crank or the trans pump. Just a thought.