Finding the centerline on a beam engine

[smfr]

I have a Stuart Beam that I've been restoring:

One issue with it is that the entablature arms are not aligned correctly; they skew off to one side. I can fix this by skimming some metal off the column and adding a shim, but it leads me to ponder how to measure whether the column, entablature and piston are all lined up. How do folks check for alignment along a centerline like this?

I have a small granite plate and height gauge, but checking this kind of alignment would require turning the whole thing on its side by fixing the base to an angle plate, I would think. Is there a better way?

Thanks!
Simon

 

[lee9966]

Mount a laser on a pivot so you can sweep it across the assembled parts?