Hell no.
My story...
12/08/08
Ordered a new alternator and serpentine belt. Thought I'd get a 100amp model that is fitted to the disco 300tdi with aircon. Would be a straight swap.
With a bit of bad research on my part and duff info gained I went ahead and got a local company to order in the wrong model which turned out to be for a 4litre V8 engine found in some defenders, but mostly P38 and disco's. Several reputable parts supplier on the internet list it as a 100amp 300tdi defender alternator so easy to be misled.
This is actually a 120amp alternator with the part number AMR4247. The mountings on the alternator are narrower and could not be modified to fit the 300tdi alloy mount points. (The distance between the mountings is only 68mm when it should be 80mm) The alternator also has an extra (4th) mounting lug.
The parts company would not entertain a return! So not willing to loose £££ and rather liking the sound of 120amp (150amp peak at 6000RPM!) I set about machining clearance on the alloy frame on the front of the 300tdi to be able to fit this model of alternator. About 10mm needed to be removed on top and bottom mount points.
A steel reinforcement ring insert needs to be replaced in the rear of the top mount, or a flat washer can be used to protect the alloy face from the alternators sliding bush when it gets tightened. When the time comes, replacement alternator will have to be of this same part number and will be a straight fit.
anyhow... up and running again.

