What cross member was cutout?

[Mike72gmc]

So I am pretty well into my frame off restoration. I have had my 72 for many years sitting with a bad motor. My truck currently has an automatic. Anywho I remembered that there was a cross member cut out by one of the previous owner(s). It is between the front end and the transmission. I have searched in forums and photo. A few seen a few pictures with trucks with them, a lot without. What is it for? Was it for an automatic or a manual? Do I need it? Is there a replacement or do I just fabricate one?

I plan to put back a 383 with around 450 horses. Mostly street driven, maybe a few passes down the 1/4 mile.