91 XJ VSS questions

so I have a manual valve body TF 904 and it does not have a VSS in it(does have a hole for one but no sensor, plug it or find one that will work?), but my Hesco standalone engine harness has a plug-in for the VSS(but nothing for the AW4), my question is: Does the ECM use the VSS signal for something other than the speedo/odometer? My harness only has a provision for a tach but I believe that signal is taken from the CPS which is why I am thinking the VSS signal is needed for the ECM to adjust..something? Anybody have any insight on this before I get too deep?

THANKS!