I don't know about a source of new pipes but I am surprised that the pipes you looked at were so corroded. I've had that pipe off on an '83 and an '84 240 and the condition of those pipes was perfect, like new. I'd guess that the owners of those cars you looked at either never changed the antifreeze or maybe the water in your location is pretty bad for engines. I'd keep looking.

The location of the corrosion you reported makes me think that there was electrolytic corrosion between two dissimilar metals, the aluminum of the pump and whatever the pipe is made of.

As far as removing those pipes, I've always been able to get them off without moving the exhaust manifold. I don't recall just how I did it but I got a small box wrench up under the manifold and took the bolt off just fine. (No, I'm not double-jointed, the opposite, in fact.)