Depending on its version i think it can be flashed to a FX5500 however you would need to get the correct BIOS for it . making sure of the following.
1. Get the same BRAND of BIOS for that card
2. Match up the memory sizes and bandwidths
3. Overclock that card to FX5500 speeds to make sure it can cope running those clocks before a flash.
As for a Volt-mod heres one for an Abit : http://forums.vr-zone.com/showthread.php?t=30238