In my case I recall 140kts at 84k. It was October 1969 and I was in F1A XM215. Can't say that I recall the Mach - the F1A did not have the combined Mach/IAS strip speed of the F3/T5/F6 and my attention was firmly on the decreasing IAS! My intention, like the others, had been to see how high this fighter pilots dream would go. Whilst going through the mid 70's discretion took over but I ran out of forward stick and so continued on upwards without daring to cancel the reheat for fear of engine surge or to roll and pull - too little IAS. To my relief, gravity and the full forward stick eventually won the day and I peaked at 84000'.
Since the Lightning was cleared to 60,000 ft. may I suggest that was very silly and I don't believe a word you say.
Even with a pressure suit, do you know how long it would take for your blood to boil at that altitude if the pressurisation failed?
You, Sir, are a Troll!!
Please feel free to PM me......