the difference has to do with the numbers in the xxx position.
215 / 50 / 16 = 24.46" tire height
215 / 55 / 16 = 25.31" tire height
205 / 55 / 16 = 24.88" tire height
205 / 50 / 16 = 24.07" tire height
If my memory serves me...
In '98 the SVT came with 205/55/16
In '99 it came with 215/50/16
same in '00
I don't know off hand what the stock dimensions were for other models though.
You're looking at .42" of height difference, yes it will make a minor difference to the speedometer depending upon what your car was origionally calibrated for.
Example
3rd Gear @ 4000rpm
215 / 50 / 16 = 49.5 mph
205 / 55 / 16 = 50.3 mph
a difference of .8 mph
I get these numbers by utilizing an Excel Spreadsheet someone on here posted a while back that does all the calculations for you when you alter tire dimensions.
