When discussing maximum speeds it needs to be made clear whether it is the maximum in level flight or in a dive. I am sure that a Spey engined F4 could not achieve 2.0M in level flight but I did manage to in a dive. The configuration was clean except for one Sparrow on a front station to keep the cg clear of the aft limit. The profile was a max reheat climb to 48,000 ft at the optimum subsonic climb Mach number (0.95M from memory) then a shallow dive (about 5 deg) to the tropopause. I managed to get 2.05M although the first time that I tried I only reached 1.95M because I started the dive from only 45,000 ft.
The really impressive speed aspect of the F4K/M was at low level. The reheat light-up time was slow but then it would reach the IAS limit of 750kts at sea level easily and with less than max reheat even in ‘C’ fit with 2 underwing tanks.