I can't really recall but don't think that I had an issue mounting the solenoid. Most ford style starter relays are pretty consistent and usually use oval shape holes to allow for variance. I just replaced one in the 6 yesterday. I will measure the hole to hole center distance and post this afternoon.
Are you sure you are looking at the correct holes? I vaguely remember there being hole for the shunt nearby. Also can't remember if I had to drill those or not.
I have found that the mounting hole dimensions can vary by manufacturer. I know I had one that had slots instead of holes to make it more of a universal fit.
Thanks Larry. The solenoid from ACS was 2" on center and the holes on my firewall are 2.5" on center. The holes are oval, but not enough.
Did see on ACS reviews that someone else had this problem. Sending it back and getting one from Van's. The one from Vans has holes that are wide enough.