The alternator would have been bolted onto the engine when the V8 was installed into the car. Unfortunately it's a long time since I owned anything with the Rover V8 fitted (and never a +8) so can't offer any advice on removing alternator.
Graham (G4FUJ)
Sold L44FOR 4/4 Giallo Fly '11 MINI Countryman Cooper D All4 '90 LR 90 SW