removing crossmember

[63burban4x4]

I have decided to use a 700r4 in my 4 wheel drive 63 suburban, with a 350 motor. I'm going to get a trans crossmember from Bowtie Overdrives. I have searched and couldn't find the thread, but I think I read on here that removing the existing bell housing mount crossmember could allow the frame to flex. That, coupled with the difficulty involved in removing the rivets holding the crossmember in (I'm not removing the body from the frame) have me wondering if I could just leave that crossmember in the truck. Will that interfere with the 700r4 install? I'm planning to run the exhaust outside the frame, so I don't think that will be a problem either way. Any thoughts on this?