The 300SD axle is just under 27 inches long, so that longer hard to get one is the wrong one for your 300TD, sounds like they have the correct shorter one in stock for you fortunately. 24 13/16ths sounds about right for a 123 chassis


Depending on what type axle it is, you will have to pop the diff cover and remove a circlip inside the diff that holds the axle in position from that side. Some have an external bolt flange on the diff side, but that will be obvious when you look under, and there is a specific name I can never remember, homokenetic or some such that differentiates them. Someone who knows im sure will post and correct me.

If you don't see that bolt flange, you must remove the diff cover to get the axle out.
I think the diff bolts are either a 13 or 14, and a hooked dental pick or small pliers are useful for grabbing the circlip inside. On the outside there is a longish hub bolt that is 10-14mm (sorry) and a punch and hammer will be useful to drive the splines out of the hub. Also a pry bar might come in handy

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