EC- and NKC-135s, with the old "water wagon" engines and a high ZFW due to onboard equipment. Wake had enough runway, but Kwaj and Midway were for emergencies only. Guam was best operationally -- huge SAC runways and available maintenance -- but for a while they were full of BUFFs doing Vietnam strikes, so we used Wake (mainly to stage for missile tests aimed at the Kwajalein lagoon).