Probably it it truer to say that the first generation neoncons, who were second or third generation new york intellectual marxists, were neocons all along rather than that they were ever serious communists. The Great Depression defined the intellectual atmosphere for years after, making marxism or some kind of drastic economic philosophy extremely tempting (see, for example, the social credit movement). So marxism, not necessarily trotskyism, was the default political attitude of the society these people grew up in; but by the 50s it was--and self-consciously--more of a moral stance than political one--for lack of something better (The Root is Man by Dwight Macdonald). The influential intellectual figures--Trilling, Clement Greenberg--were still saturated in marxists (or hegelian) ideas, despite having moved away from any active political engagement, and they still maintained a generic radical stance, in opposition to mass culture and mainstream politics. The next generation (Irving Kristol born in 1920; Podhoretz, 1930) adopted this already diluted position, because it was the conventional one of high brow intellectuals, without really having to commit, as their mentors once did, to radicalism. The marxism of the 50s was an increasingly inappropriate posture, and unsurprisingly did not survive contact with real domestic political turmoil. It was the very complacency of their academic Marxism that allowed them to be "mugged by reality" in the first place. This also meant it wasn't an especially difficult decision to give it up. Podhoretz had been criticized as genteel and insincere before he ever gave up his modernist pose, and Harold Rosenberg, some kind of individualist, wrote a lot about politics in the 50s being used as a cheap route to seriousness, leading to a non-critical, dishonest conformity--insincere marxism (The Tradition of the New). Dwight Macdonald, who probably occupied every position on the map at some point, also wrote some highly dismissive stuff on the rising political generation--criticizing both the National Review and Irving Howe's Dissent for being drab, self-serious affairs, filled with cant, i.e., lacking the genuine trotskyite bite (something he had first hand experience with; Trotsky himself supposedly declared: "Every man has a right to be stupid, but comrade Macdonald abuses the privilege.”).

Generally, a common cause between conservatism and communism had been vaguely acknowledged at the start of the century--that is, both hated commercialised society. cf. the incestuous relationship between the partisan review crew and new criticism, the latter run by southern reactionaries like Allen Tate. T.S. Eliot and Santayana both expressed a greater willingness to turn Marxist before turning liberal, in the social democratic sense of the word. Podhoretz, who came up in a literary tradition (his mentors were F.R. Leavis and Trilling), was an academic before he was an activist, and him ending up as a conservative was just a matter of admitting he cared more for the "seriousness" of T.S. Eliot's literary criterion (the puritanical influence of which it is impossible to overstate) than for the relativism that liberalism entails (he took the moral high ground against the beats in the 50s).

The emphasis on social values in the 60s, not economic or nationalist, really brought home what liberalism meant, beyond the distractions of war and poverty, the victims of which are much easier to sympathise with, the crimes easier to identify. (not saying war and poverty were not major issues in the 60s; they just weren't totalizing).

Actually, I'd say it is only in their acceptance of commercialism, not rejection of communism, that the neocons really changed their mind, and subverted their intellectual heritage. (Interestingly, this was not accompanied by a respect for popular culture, which was still pinned on permissive liberalism, not acknowledged as a by-product of free market capitalism).

So I'd guess that the trotskyite influence on modern neocons is minimal. There is perhaps a latent hegelianism, in their admiration of power and aggresive patriotism, but these ideas don't need books to suggest them (Fukuyama's end of history is explicitly hegelian, however). You could make a fun analogy between the hegelian critical approach that Eliot and Greenberg took towards the chaos of Joyce and Pollock and the idea of the free market (creative destruction, the invisible hand, etc.)--that there is a method underpinning the madness. corruption is accountability.