Please see the other replies on this, but no there is no way to do policies like this in 6.X like there is in 7.X. For us, it was not needed in 6.X, it just worked. We did require the change on the 7.X side.
We just ran into this exact problem today. One wanscaler was behind a PIX 6.3 firewall, and the other behind an ASA with version 7.X.We found that the version 7 needed the above configuration, but the version 6 did not.I could not find anywhere to s...