Older OBS to LS wire harness setup

[1991SSP]

are you going with cable drive or drive by wire?

Your most simple option is to take your donor harness for the LS engine and make it into a stand alone.. you will need to put your oil pressure sensor from the old engine onto the LS with the proper adapter.. you will need to re use the temp gauge sending unit wire that was plugged into the driver side head and proper sensor onto the LS engine.. you can use the speedo output wire from the new LS pcm and run it directly to the speedo wire at the cluster,,, the new PCM should have a MIL wire too that can be ran straight to the cluster... your setup as far as wiring should be pretty simple as long as you are comfortable and can read schematics

you should be fine with putting the VSS plug from your old trans onto your new harness, I believe they are the same