Well .... The water pump on a small-block chevy is bolted to the block via two bolts at each side (the legs that run out a couple inches to each side from the center of the pump body, to the front of the block). These four bolt are all that secures the pump to the engine. Other than this, you just have the hoses.
As for access, I am not familiar with the 2003 Horizon, but on our 97 245 Sunbdowner you could remove the whole fiberglass engine surround housing (a dozen screws, or so). With the housing removed, it looked like this:

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Gordon Arnold
New Hampshire
2003 268 Vista ..................................................................Prior: 97 245 Sundowner
