Need 240V in the shop, is it already in this OLD panel box?

That's crazy. For the amount of work it takes to get the wire routed and the minimal cost why the owner did step up the gauge to atleast #8 is beyond me. I personally would pull a #6 depending on the conduit.

The good news is you can easily make the changeover. However if you are not comfortable with AC voltage work find someone who is to help out.

Good luck,
JW