Just got done with new 400 engine install the engine turns over perfect untill i get it attached to the c6 transmission then it locks up i have had the engine in and out three times trying to see what kind of bind i was in but i get it all lined up and in and the engine tightens right up and will not turn over. any ideas trans problem tourqe problem

 

Something has to be jamming the starter or flywheel. Could your torque converter not be properly engaged with the front pump of the trans?