You'll probably end up with a good-sized hole in the transmission tunnel. As for the rods, I'm not entirely sure what'll be involved. If they need to go longer, you may be able to cut them on the long, straight sections and weld in sections of heavy-wall tube to put things where they need to be.
I got the same thing from Super Shops when I bought one, but never found it to be that difficult to downshift. I quickly developed the habit of downshifting by placing my thumb on top of the T-handle, lifting the trigger with the middle and ring fingers and pushing/pulling the handle as needed. It's a little weird, but well worth the oops proofing that the mechanism affords. It was also fun to watch windshield repair guys struggle to move the car into a bay. There was a lot of "Hey, man. Where's reverse on this thing?" involved. 8)