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The Softrock uses a crystal that is approximately four times the frequency
you want to receive. It has to be a fundamental mode crystal; the
oscillator circuit is not designed for overtone crystals. That is divided
by four by the divider circuit that generates the quadrature signals. The
30 and 20 meter versions, and some of the IF versions, use 1/3 subharmonic
sampling because fundamental mode crystals for the necessary frequencies
were not readily available at the time.

The crystal frequencies used in the Softrock kits for IF frequencies are
listed on this page:
They were all
chosen from crystals that could be bought as stock. No option for 9 MHz is
listed, but the 9.015 is close enough, and the required 11.98135 MHz
crystal is still available from Digi-Key and Mouser.

An alternative that is possible now, but which wasn't at the time that Tony
Parks designed the kit, would be to use a 36 MHz crystal. You would have to
move it at least 20 kHz away from that nominal frequency (either side will
do) so that the LO would end up 5 kHz away. You can probably get it moved
that far by adjusting the load capacitance. 36 MHz fundamental mode
crystals are now available, though only in SMD packages.

One further note: the IF of your TenTec is probably not EXACTLY at 9 MHz.
It actually depends on the specific crystals in the filter and varies with
component tolerances; the rig was aligned to match the actual filter. So
the signals in your Softrock could appear in a slightly different place
than you expect.