I am ready to finish machine the bore holes in my sl/6 torque plate. Any recommendations for the finish bore size?

lanctof@wsdot.wa.gov

This really depends on what you will use the plate on.

For cast iron SL6 blocks, I would say 3.505 to 3.510 would give you over bore ability into the 3.5 range.
(most head gaskets have a 3.5 opening)

For the Alm. Block SL6 you need a 3.445 to 3.450 max plate, you just cant bore these engines as far and you need good contact around the tops of the cylinders.
DD