Word on the street is it's not necessary in the short term as build 11A494 once installed is the same as 11A511 (& same as the final GM seed).
If you still want to do something today (and don't want to hold the option key down when clicking purchase to bypass the App Store check) - I would install Snow Leopard to a spare partition or USB drive and do the purchase / download from there.
At that point, you can erase / restore / install as desired. Worst case, you'll have to wait for instructions or migrate your GM system to a fresh new install.
In the mean time - we can pick apart the manifest and pre-flight script for Lion ;-)