It's been several years since I had a Smith disassembled but as I recall, the return spring is putting a healthy side load on the top lever shaft. This is what you are fighting in order to re-assemble the gun when you put it back into the stock. I'm assuming your gun is still apart and the bottom of the top lever shaft is still unsupported.
A couple years ago, I posted some tips for re-assembly that I read either in Brownells Gunsmith Kinks or Brophys' L. C. Smith Shotguns. The one that was surmised to have been used at the factory has worked well for me. Perhaps you could do a search here and find it.
