How do you center vocals and expand the music sound stage on a mono recording

I have a 1972 mono music video concert recording rarity with vocals that I want to expand the soundstage using the stereo expansion function to give it more of a "stereo effect".

I tried great room reverb with 2000 ms delay and the wide stereo expansion setting in the rack. when i do that, the the vocals disperse, do not sound as clear, and centered. the music sounds great though and is what I am after. Great room reverb alone is not enough.

what is the best process to center the vocals while at the same time expand the music sound stage with a mono recording.

thanks

Rick