Mike,
Found these past comments (searched for "neutral safety switch").
"You will have to stick your head up under the dash and look on to of the steering column for the Neutral safety switch.You will just see the top portion of the switch.The bottom part is down in the column.Part of the switch should move left or right.Grab the top portion of the switch and slide it to the right a hair,then see if b/u lights work if not try other positions a little at a time."
"Take the driver side under dash panel off .Look on top of the steering column for the neutral safety switch.It's white and about 3"-4" across.The top portion of the switch slides left or right.Try sliding it about 1/8 in.-1/4in."
HTH
Mickey