First get the center to drive axle to center of front bolt dimension from John at Pro-Line. Best way to install is to have the sled on the ground, with motor in and ski's on. Support the back bumper with a jack or strap of some sort to allow you to move it up and down. estimate your ride height with the suspension setting on the floor underneath it. Once you get your front hole located, drill it and bolt the front of the skid in the tunnel. Then repleat above to locate your back mounting hole. You will also need to get a rough center to center torque arm mounting dimension from John also. What generation proline skid do you have? He's had about 5 different one's in the past 6-7 years.
Buddy P