Equipment lock will keep you in the airplane. The company has waived it in the past, but that seems to have been a one time deal. Future staffing needs might change that.
That being said, however, I wouldn't recommend attempting a left seat upgrade into steam gauges after having flown glass... Individual results may vary, but I think you'll find it quite difficult. Most people do.
Guess it depends on your background or something. I upgraded to the DC10 from B757 an didnt blink .There were 10 guys in my class 5 757 and 5 320 none had a problem.