That style Chevy is one of my favorites (a very close second behind the mid 80's trucks). I love the two tone too. I think you'll be pleased with the V8 that is in there, especially since it's a newer version of the original.
For sag in the rear, I would recommend putting some Air Lift air bags in the rear. I had them on one of my trucks and absolutely loved them.
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'05 Sea Ray 185 Sport