I tried loading the ROM into Polaris editor (v 1.4) but it complained that the ROM was not 512kb (my card uses 256kb ROMs) and the values loaded made no sense. Polaris editor thought my card vendor id was 0x5249 when that is in fact the last two bytes of the PCIR signature, the other values also looked off (2000 Mhz is not the card’s max frequency!) so I did not risk using it:
Also the method I detailed above resulted in a bios that did not require use of the ati pixel patcher, which for simplicity I would prefer not to have to use.