As MechE said, ford made an ign. change. i think that was in 99.
Wanted to install tach. on my 99SC XL. Last time i checked maybe 1yr. or less ago?
Autometer....did not have a tach. guage that would work on these new ign. systems...99 & newer. said they didnt have the new technology etc...so
They said try paulshp.com Dont know if that site is still up, but i did check....he had parts that apparently would work but for me to much $$$
There was another Co. that had parts that might work, sorry i cant recall name...Member here IanN from Canada, posted that name...
OEM instru. panel from Ford with the tach was available but no install instructions. Service dept. said they just use the existing wires and had no info. re: if it did not come with a OEM tach...would have to remove instru. panel, see if tach wire was there.... Of course if they do that well $$$ & new guage panel was somewhere around 500.00.... And, that wire does come from the PCM.. At least thats what they told me.. I could look for wire, etc, but cluster to much $.....
Anyhow, learned to drive with out dash tach....Sometimes i use the dash digital Odometer when i really want to know how many RPMs im turning.
Maybe someone here has already done it?
I just put the tach $ into other mods
Good luck. OT