Please see the How to thread about installing headers. Search my name and "ea sy" without the space.

I have never used RTV and would hate to clean it if you ever pull them off again. FrozenBoost has the clamps for cheap. 2 x 3.00" and 2 x 2.25" IIRC. I'd swap the flex as well.. if you want to remove the drain trap, somewhere I posted pics of a jig that can be used to cut/reweld them.