I think the Afican Opel Boss (or Superboss) was the only GM car to have LSD fitted as standard in a F28. Unfourtunalty you can see this in EPC, which is shame.
I bought a F28 which had alreadybeen converted to 2WD via one of those kits shown above. It hasn't got a gasket so white silicon selant was used which has squirted out all over the place. Plus one of the bolts looks wonky, in that it hasn't apeard to have been screwed in stright, so a re-tap or helicoil is required proabaly.
Anyway, its all being sorted out by www.v-tuning.co.uk to have the 2WD converiosn redone and LSD fitted.