Prepping factory k-member for race duty

Hello, I am getting my front end ready for my big block, it's a 70 slant 6. I've got the entire steering linkage brakes & k-member out of the car.
I have a milodon super stock oil pan and I assume I'll have to do some trimming & reboxing in also weld the seam & remove unnecessary mounts for my application.
Anybody have an idea how far into the center I'd have to cut. I imagine 3 inches would be plenty of clearance, anyways looking for opinions & pics, not looking to go tubular (yet)