Can90 managed to get me a network capture to look through, unfortunately it doesn't contain a reference to the stock rom. I assume this is because LG just hasn't uploaded it yet.
For anyone that wants to play with URLs to try and find it, this is the relevant portion of the response to lg's updater app.
<model>LGVS750SS</model>
<suffix>AVRZDB</suffix>
<esn_date>20100420</esn_date>
<sw_version />
<sw_url />
<sw_locale_url>/</sw_locale_url>
<sw_recommand_uri>AIC/GLOBAL</sw_recommand_uri>
<app_version />
<app_url />
<cs_em_flag>N</cs_em_flag>
<cs_em_uri>N</cs_em_uri>
<chip_type />
normally sw_url and sw_locale_url would have what we want, but they're empty