I'm unsure about E759, E762 and E770, but E760 and the black X58-SLI definitely need the mod. We had quite the drama in PCGHX when someone recommended a Xeon to someone with Evga SLI and it didn't work... the E760 I tested myself.
Afaik some of the later PCB-revision run Westmere EP without mods as well. Asus and Gigabyte are the safest bet, never heard of problems with those.