As far as Black Top goes, I'd shoot for ~7% ABV with 40 IBUs. It's probably a restrained version on the style which may account for its popularity. I'm not sure what dark grain you'd use for the color and roast/chocolate (Black, Chocolate, dehusked Carafa) but you could take the name of the beer "Black Top" quite literally as the addition of your dark malt "on top" of the mash (if doing all-grain or partial) after it is completed. In other words, you would mash your other grains as usual and at the end of the prescribed time, add your dark malts, and drain/sparge as usual. You may also choose to "cold steep" your dark malts overnight on the side and add to your wort before or during your boil. There are a lot of ways to experiment with this, and it all depends on your tastes.
As for the hops/recipe, I'd start with jwm's recipe for Moon Man if you have access to those hops and add about 5% dark malt. Keep it simple. I don't remember it being a terribly black beer but definitely darker than a brown. There is a definite tropical fruit nose/flavor to the beer so use hops that harbor that quality.
*EDIT* Some further searching suggests that Chinook, Amarillo and Citra are used. If I was making this I'd tend to favor heavier late additions, perhaps a blend of all three, the ratio up to you! I got more Citra in the nose.