On my Escalade 6.0L swap I wanted enough room to for the 2002 Caddy top engine cover to fit. I wanted the "Made Exclusively for Cadillac" to be visible. In 02 only the Escalade had an LQ9. Chevies got it 03.
So I modified the engine portion of the Fleabay mounts to lower the front of the engine. Surprisingly is created more room at the rear of the crossmember. Now there's nearly 1/2" to the pan at the back of the front crossmember. And the pan is about 1/2" above the front of the crossmember. If your pan is farther away there is room to go down. I think BK is correct that you might want to put a different rear mount that's taller in there. I have a 4L80E so I can't help with which one to use. Maybe one from a 2wd Silverado 1500 with a 4l60e? Or you can cut a plate of 1/4" or 3/8" steel to put between your trans mount and the tail housing. Use a stack of washers temporarily to find the best height. Or simple stick a piece of 1x2 in there to see if it cures the problem. That's 3/4" thick. or try a 1/2" plywood scrap.
Here's a Photoshop image of what I did using your pic.