You can slo look at the sticker inside the door frame and tell what you have also.
Any truck built after December of 1997,except for the 7 dealer display show trucks with 24v in them built in October,are all 24v's. There were 7 built in October of 1997 which had the "new" 24v motor in them for show and dealer display purposes. One of those 7 is here in Central PA and owned by a TDR members wife.