Jack
The GR1 never had its ramp intakes connected so M1.15 was about its top-end - unlike F3 which did have the ramps connected and could make M2.0 (M2.15 was my personal best in a jet straight off the tanker with no LAUs fitted). So 1,700mph+ is plain wrong. At low level 920mph would be possible in a GR1 with the smaller engines and I've been at 870kts at low level in a F3 with 2 winders and 2 skyflash and only the crew becoming the limiting factor (chicken!) - again the F3 was quicker than the GR1 at low level, but it should give you an idea.
As for range, the internal fuel of a GR1 is about 5100kgs and an average fuel burn of about 50-60kgs per minute at medium level at around 360-400kts TAS - so that would give you about 100 minutes at around 6-7nm per minute or a range of about 600-700nm. Again the F3 had an O-tank fitted behind the nav's head that gave about another 10-15 minutes of internal fuel - or enough for burner take off and climb to 10-15kft before cracking into the normal fuel tanks that both types shared.
Now the GR4 has different engines, 1 gun less and a different drag profile underneath so it would be different in performance to the GR1 - plus as M2 says this is a current type so it's off limits for discussion.
I hope this helps?
LJ