Speedometer cable

How do I know which speedometer cable to get. I go on 50Resto and it has too options, with speed sensor and without, how do I know which to get. Also how do I install it, is it simple? Its a 88 mustang GT with the stock 85 mph gauge. 3:73 gears.
Thx for advice.

replacing a speedometer cable if very easy. you take the dash apart, unscrew the speedo and pull it from the dash. you then disconect the cable housing from the speedo and pull the cable out. wipe off the old lube and then lube the new cable. insert the cable into the housing and turn it so that it engages the speedo driven gear. I suggest getting a chilton or haynes. it will show you step by step and is very simple to do. 15 min job. as far as speedo sensor I'm not sure if you can tell without removing the speedo from the dash.