Transmission crossmember question

[phil g]

I am in the process of swapping an auto tranny in place of a three speed tranny. I have an auto crossmember, column and other necessary parts.
Will I need to remove the manual transmission crossmember to make this swap work? I realize it would look neater, but removing the upper rivets in the crossmember looks like a real pain. The truck is a 70 model C-10 and will never be anything a driver. Any input will be appreciated.