Chuck wrote:
I too had to fiddle quite a bit to get the extension table in the same
plane as the cast iron top, but it can be done.

Assemble the table to the wing with the bolts just snug, but not fully
tightened up yet.

Take a straight piece of wood about 2 feet long (a 2x4 with one wide face
jointed flat would work just fine) and lay it along the front edge of the
table, overlapping the joint. Clamp it to the cast iron wing with a couple
of C-clamps. Do the same for the extension. Repeat the whole deal along
the rear edge of the table.

You have now just forced the table joint into perfect alignment. Tighten
up the bolts holding the extension to the cast top, remove the clamps, and
you're all set.