67-72 Frame cross members

[drive.1968]

Hello all,
I am building a 68 SWB with no markers. I have decided to use the frame that has the the least damage and already has disc brakes, however I realized that this frame has an extra cross member directly under the fire wall. It is riveted in so it is a factory modification. Is this extra cross member between the front A frame mount and the transmission mount needed? It appears to be directly where the engine flywheel will mount to the the turbo 400!!! Was this mount for a straight six engine? I have went through the Chevrolet Truck Chassis Service Manual and it does not call out this particular mount and this mount is not on my 68 LWB that came with 307 and a turbo 400 transmission.