Got any V blocks ?

If so lay it in the blocks, clock it with your dial gauge, note the measurement, turn it 1/4 turn and keep repeating.

If you can take all the gears off the shaft roll it over a flat surface such a piece of plate glass - you will see if it is bent.

Put it in the chuck of your pillar drill if you have one, clock it while turning by hand. Probably too big for the chuck though !

All a bit basic but might give you an idea.

No doubt someone will come up with other ideas.