While removing the transmission I discovered a small coolant leak from the front of the tube that runs along the right side of the engine. I can't find any reference to this tube in either the Haynes manual or the Suzuki factory manual. Is the tube part of the engine block or is there a seal on the front of it? Does anyone have an exploded parts diagram of a 1988 Samurai that shows all the bits and pieces and what their proper names are? How do I replace this tube and are replacement ones available?

that tube has an o-ring on it that sticks in the water pump. there is one bolt to the block that holds it in place.
i think replacement tubes are available - probably called 'water pump tube'?
sounds like that o-ring is leaking.
should be under cooling in the manual(i don't have the whole thing).
sorry

If you are in a northern state the coolant manifold can be rather corroded so check it out before putting it back in.

  Thanks for the info. I did locate replacement parts at Petroworks. A new tube is $105 . I  ordered a new seal for it and hope it will seal up.

Give Hawk a call and I am sure they can find you a very useable used one for far less than 100$ !!!