Won't crank?
i have a friend that had a similar situation when he first put in his 360,he looked under the car to find out that the old starter gear was misaligned somehow(the gear slides back and forward)and until he got a new starter,when his car would do this,he would reach under the car and manually adjust the gear,maybe thats it? it made a clank like youre describing and wouldnt turn the motor,then he would adjust it and it would start right up,hope that may help