Need some info on front frame clip for straight axle 57 Chevy

I am in the process of swapping over to the speedway axle kit on my 57 and one of the things I havent seen addressed is the insert on the frame for the gear box bolts. I am under the ***umption that you would want the new tubing to slide in a ways. Just curious how others have done this. Frame is already cut and ready to be prepped for welding. I am using the original gear box with a cross steer set up.