From MOONPORT, NASA's journal on how the Kennedy Space Center was Made. The Crawler-Transporter was never considered during the initial studies. The Debus-Davis report concentrated on the rail concept, but the stresses and cost of building the route to be excessive. There was consideration of building a canal system to barge the launch vehicle (The actual LV was still under design) which also had its risks.
It was not until 1962, Albert Zeiler pegged on a proposal by Bucyrus-Erie for a Crawler-Transporter concept. At the time, the rail transport as well as the barge proposals were on the ropes due to major engineering problems.
23 March, B-E contacted the LOD and gave a cost estimate. Thomas Learmont, Bucyrus-Erie's chief design engineer, provided tentative estimates: the crawler, jacks, hydraulic system, and steering mechanisms would cost $3,650,000, the umbilical tower $1,500,000, the box structure (launch platform) $800,000.
On 12-13 June, a LOD conference with industry execs and NASA officials, the Crawler-Transporter was approved for production. B-E was up to their eyeballs in building the worlds largest tracked vehicle.