Telstar, as Del P mentions all it takes is a quick word on the r/t and any speed different from the "norm" will be easily accomodated.
Ideally get the call in before you're on base leg as it's the base to final turn timing that dictates the spacing on final.
There was a time when some 737 operators seemed to prefer 170 to 5. The only problem that caused ATC was that it wasn't applied consistently across airlines or similar types. Perhaps the one thing that is really necessary for tight spacing and high landing rates is everyone doing the same thing for the last 15 miles or so of the approach. Too many variables and capacity is reduced.