Desilu picked up the proposition and together with [Gene] Roddenberry, the studio executives made the rounds of the television networks to reciprocally pitch the proposition to them, ultimately finding Solow's former employer NBC interested in early May 1964. Prior to this pitch, it was [Oscar] Katz who took Roddenberry to CBS, the network that traditionally aired Desilu's television productions, but, not backed-up on that occasion by Katz (already foreshadowing things to come), Roddenberry seriously botched his presentation on that occasion.
Dismayed, as CBS represented the best chance Star Trek had, due to the network's longstanding relationship with Desilu (CBS aired [Lucille] Ball's own I Love Lucy show), Solow subsequently took over after being informed of this. He thoroughly groomed, prepared, and coached Roddenberry for his next, very last-chance, meeting with NBC the following month, as well as taking an active part in the presentation. Additionally, Solow instructed Roddenberry to keep quiet when not required to speak (which, given Roddenberry's predilection to the contrary, was excruciating for him), as NBC was wary due to their previous dealings with Roddenberry on The Lieutenant, and, most notably, to drop the "Wagon Train To The Stars" pitch-line Roddenberry had used on the previous pitching occasions. This eventually resulted in success, but "(i)t was Herb's tenacity and Herb's presentation that sold the series," as NBC executive Jerry Stanley later conceded.
Solow was subsequently heavily involved with the studio oversight and marketing to NBC of the two pilot episodes, "The Cage" and "Where No Man Has Gone Before". While not a science fiction fan, Solow strongly believed in Roddenberry's format, which he considered a more adult counter balance to the somewhat juvenile Lost in Space series of CBS. After the production of the two pilot episodes and after NBC had in effect ordered the series, Solow had to vigorously defend Star Trek in early February 1966 before Desilu's conservative Board of Executives who, balking at the costs of three expensive series in development, virtually unanimously, save for executive Bernard Weitzman, wanted to proceed with Mission: Impossible and The Long Hunt of April Savage (also brought in for Desilu by Katz and Solow, the former ordered by CBS, and the latter, also produced by Roddenberry, ordered by ABC) only. Katz was also a board member, but was not present as he was already on his way out. Fortunately, Solow – unlike Katz not a board member, nor would he ever be – managed to get the studio head, Lucille Ball, on his side and who, as Chairwoman had the power to overrule her board, which she did by approving the continuation of Star Trek with a mere nod towards Solow, or as author Marc Cushman had put it succinctly, "That was all Star Trek needed. A nod of Lucille Ball."
They changed the registry of the Discoball when they refitted it - it's now the NCC-1031-A. Why you might ask? Good question. Every* other time in Trek history where a naval construction contract number was reused (NCC-1701 being the major example) the letter was appended for a new vessel of the same name. Which is why the refitted Enterprise from the first film retained NCC-1701 as her registry number, because she was a refit rather than an all-new build (