I'm running a th400 trans. In my case it is way more easy to keep the existing trans and bold the new motor up to it. If you had a 700r4 it would be whatever way you wanted to go with it. New motor would bolt right to the old trans or tys new trans would bolt right to the old t case. As far as headers, there Is a thread on here about what hits and what fits. My stock 5.3 manifolds fit fine but it looks like 6.0 manifolds are different and will hit. Only thing I have to do on mine is modify the down pipe off the manifold to clear the bottom of the frame.
Got the new harness a little but installed last night!
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