You have to cut for the side of the shifter body to come through the side of the tunnel. The top of the body comes through about 2 inches and that protruding body then tapers down as the tunnel runs out towards the floor. The cut must run down below the lower tabs of the shifter body and then you have the 3/4 rod that attaches on the outer leg. That shift rod then needs the floor cut for at least 4"-5" forward of the shifter and it needs about 3/4" relief for the rod to not be in contact with the tunnel. I am sure you could pound that out with a big hammer, but I'd rather cut it than pound it out. Here's a picture that shows how much of the body is going to be sticking through.
I don't think the big block is that much different from a small block in terms of tranny positioning is it? Like maybe 1/4" or something? In either case, this shifter mount locates the body up high and needs relief cuts in the top of the tunnel and through the driver's side or the shifter isn't going to fit. You can maybe close it in tighter and negate making the box as I did, but then you need to wrap a large boot down and around the side of the tunnel which I don't like the looks of? Unfortunately, I didn't see any shortcuts in how to do this right and did what I could to close it in while keeping it neat.
The current model Super Shifters have smaller diameter shifter rods but they are weaker design than the older ones like I have here. I'm pretty sure the Super Shifters have always used this particular mount, but as I have done in the past, there are ways to mount it down low using a different mount and the lighter offset shift rods. That means less cutting but don't think the functionality is as good with those modifications.
FWIW...I'm no expert at this. Just doing what I can with what I have here and pretty happy with how it's turning out so far.
