When I had my 97 L lifted and running 205/75r15s my speedo would read 55 when my gps speed was 60. My tires were slightly taller than yours so I was a little more off. Best way to see how far yours is off would be to use a gps enabled device like a smartphone or the like and one of the many apps available to give your gps speed and reference it to the speedo.

we are going to do some Balck Friday running today so I will take the GPS along to see what the exact speed is.    I wanted to go junkyarding but Karen has other ideas..... 

checked the speed with the GPS, speed is actually 3 to 5 mph faster on the GPS than on the speedo.  At 69 mph the GPS read 71 mph.  At 55mph the GPS read 59 mph. 

That's about what we expected it to be off, always safe to check for yourself though.

"It is a 95 Legacy LS, Auto, sunroof, power all,  2.2 motor."

 

My son has the same car, of course with the standard suspension. I really like driving that car. The engine leaks some oil, but runs fine at probably around 179k miles. Interesting when you see a $40k Audi or Acura spinning it's front wheels in snow trying to go up the hill to the local mall. My son's $2,200 Legacy (cost in 2011) would pass them.