I agree with LOMCEVAKS numbers but would add that if approaching the Trop too quickly it was possible to make a second climb once above M1.03 (Ramps travelled) back up to 45,000ft and then a 5 deg dive would achieve M2.0+.
Also agree that the F4K/M would easily reach 750kts at low level. I have to admit accidentally reaching 795kts chasing some USAF F111s over the North Sea before noticing the speed. Fortunately the tanks stayed on and there was no damage. Any way, as a Flying Officer my "top cover" was my Flt Cdr in the RCP.