I went to AutoZone and purchased a new starter for a 2010 LS3 6.2. Bolts right up and gives me the clearance I need for the header flange with no heat shield on the solenoid. Even with a shield I think it would work.
Still, looking at the pics below I'm not comfortable with whether the starter would actually function properly and I don't really want to jump it in place as pinion gear might get scarred preventing me from returning it.
Oddly the new starter pinion gear seams to be the same diameter and tooth dimensions as the stock 2001 LM7 5.3 but the new has 10 teeth and the stock 11. That does not make sense to me. If they were different diameters I could understand how 10 vs 11 could work. But as it is I hesitate to use a LS3 starter. I have read that a LS3 flex plate is different than a LM7 plate but I don't know how it is different.
Unless someone on here can confirm that the LS3 starter will work, I think I'll go the safe route and clearance the frame boxing plate (have to do that either way) and grind the starter side of the flange and dimple the heat shield.