Talked with Mike over at Comp Cams today and he said use the stock 7.4 pushrod with the LS6 heads just like you said Greg. I'm going to install the 7.4's and just make sure it's centered across the top of the valve stem.

The best check for the LS6 cam will be to do the same. If you're not centered across the top of the valve stem you will have to go with 7.45's. They said it could go either way depending on your configuration.