[brcidd]

Your harmonic balancer is shot...rubber has torn loose between pulley and hub- classic symptoms are a knocking noise on start-up and shut-down- just as you describe. You have diagnosed correctly, now change it out- takes a puller on later model engines, as is yours. Not a bad job. In fact you can practice, using your donor engine first.

Hardest thing is breaking the crankshaft bolt loose- I have used a breakerbar mounted against the frame rail and used the car's starter to break it loose. Works even when an impact gun won't.