I believe Omega's two (now one?) 7-O's are Boeing 707-320's (stretched) with the original (but upgraded) JT4A series turbojets ... which originally meant their MTOW is probably in the area of 310,000# ...
They have advertised their fuel capacity as @155,000 - 160,000 # ... so if you figure @ 145,000 BOW and @155K +/- FOB -- you're looking at @ 300K +/- TOW ...
They also advertise: "At maximum landing weight, Omega can land with about 100k of fuel, so unless the flight is very short or has a low planned offload, Omega can usually takeoff with full fuel. On a 10,000 ft. sea level runway, Omega can takeoff with full fuel up to about 85 degrees F ..."
Yesterday's "mean" WX @ MUGU was 56 degrees, with a high of 63 degrees in the afternoon. The winds varied all day in the range of 11-32 KTS from the WNW, altimeter @ 29.81 ...