Joe, there is a strong probability that the valve block you seek
was intentionally removed in the course of a tracking system upgrade.
If your double tracking pneumatic has three tubing connections, it
is the later improved type and doesn't need the valve block.  If you
still have the old type with only two nipples or elbows, I can send
you a tubing diagram showing how to make it work just as well without
the valves.

Normally in the course of an upgrade a cutout pouch block was added
between the tracking pneumatic and tracker ears.  This prevents the
pneumatic from moving in the wrong direction during reroll.  Instead,
it automatically centers itself being under continuous exhaust with
suction equal in both chambers -- an improvement even though there is
no provision to accommodate the small variation in the depth of right
flange bearing shoulders encountered from roll to roll.

Jeffrey R. Wood