There is an advanced way to get a ROM "dump" from a phone, but I don't know how to do it.
Not sure what you mean by "serial" from your phone.
If you build with PPCGeeks Build OS, you can recreate the ROM by rebuilding from your specific selections.txt file. Also, the ROM can be copied from My Document\BuildOS RUU\RUU_signed.nbh, which is overwritten each time you build a different ROM.
I would suggest trying some other ROMs built with BuildOS. I recommend
http://forum.ppcgeeks.com/showthread.php?t=46525
and
http://forum.ppcgeeks.com/showthread.php?t=53781&page=3
I used to keep older ROMs, but find that for the most part, I keep going forward, not backward to old ROMS.
Not sure this will help you much, but it is all I have.
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"One is glad to be of service." Bicentennial Man
Verizon: XV6700, XV6800 w/ROMs cooked in PPCGeeks Kitchen, Omnia i910 with cac2us ROM and Omnia 2 with Ninja4Hire's ROMS.