Why's your ABS on? Have you tried replacing your speed sensor in the rear on the top of the diff?
If you want to get it as close as you can you'll have to pop off the plastic cover for the gauges, pop off the needle for the speedo, get a gps, got say 20 or 30 on a LONG straight road (helps to have a friend with you) and place the needle on the speed the gps says... That's what we did with my buddys truck we just did a few weeks back with the red lense repair tape and some red leds...
btw, lets see some pics of the dash!
FXEdgeplorer Level II
Part 01, 02, 03, and 06
Tall, Slow, Shiny, Loud
6 Lug Ranger
D44 SAS'd on 12" of lift and 37's...