The best place to farm Shredder Operating Manual - Page 3 is Ashenvale, where Bloodtooth Guard (level 27-28) drops it at 1.5%. That is the vanilla 1.12 chance, not yet confirmed in Forever. 85 sources are ranked below by drop chance.
Gold per kill: Bloodtooth Guard is worth about 2s 85c a kill in item drops (at Auction House prices). Gold farming spots, level 20-30
Best zones:

- Mugglefin 19.4, 42.7
- Wandering Protector 65.4, 44.0
- Akkrilus 25.6, 63.5
- Eck'alom 52.7, 70.1
- Rorgish Jowl 35.8, 36.6
- Bloodtooth Guard 54.7, 79.3
- Dark Strand Enforcer 31.6, 31.1
- Saltspittle Warrior 21.3, 42.9
All sources, by drop chance:
Drop% is the rate recorded in Forever once a source has been looted ten times; a greyed figure is the vanilla 1.12 chance from the world data (classic data: from the patch 1.12 world data, not yet confirmed in forever). Spawns counts the source's spawn points in the world data. "Side" names which side can kill the NPC when the other finds it friendly. The lead picks the best chance among sources that are not a rare spawn and have at least three spawn points.