1985 BMW 325e engine knock

1985 325e--250 000kms, 2.7liter inline6 5speed.

My engine has developed a knocking sound, like tapping a wrench on metal. I 've replaced the plugs, cap and rotor, fuel filter, and fuel pump recently. There is no indication of low oil pressure and I have no oil leaks. The car seems to pull strong despite the knocking. It is present during idle up to 2500rpm or so, after that its still there but harder to tell as the speed of the engine increases. It almost sounds like a rabbit diesel at times! It has been suggested to me that the rod bearings are worn an that I do an inframe rebuild on the bottom end. What do you think?