Replaced main bearings and conecting rod bearings now motor wont turn over

You should be able to move the caps & rods on the bearings there will be some float check each if on is not moving back it off and see if the engine will turn by hand, did you check the oil clearance when fitting the bearings why did they need replacing? Did you damage a journal with a faulty bearing?

I replaced bearings cuz one started to knock come to find out one connecting rod bearing was verry thin checked end play and all are tight except for # 3 cylinder end play was right about.012 close to limit would you say re check clearences or pull motor and rebuild

You will need to at least check journal dia and condition, if not to specs a grind will be required.