No...
It will not read correctly if you swap the face. If you put the 145mph face on a 120mph speedometer it will still function as a 120mph speedometer and the needle won't point to the correct speed on the 145mph face. The heads are geared differently. If you need a new 145mph head, I believe the speedo's from the 3.0L or 3.2L Taurus SHO will work (I heard that somewhere) and they are generally available on ebay. There is a slight difference in the illumination color between the SC and SHO speedo's, but if you swap the face, that should fix that.