I would be careful using this method, its not real accurate, I DO NOT mean to be disrespectful, just HELPFUL . You are squaring the housing to the rear cross bar located 10-12 inches apart. if you are off a 1/16th or the bar is off a 1/16th the error is greatly amplified by the time you reach the front area of the car. being out a 1/16 will effect the car, amplifying that number will make a much bigger difference. I plumb bobbed cars for a long time as you are, it is ok, but I found out later its not that accurate and you are not squaring the rear to the front area of the car. I have spent alot of money on expensive lasers and can tell you squaring to the rear cross member will probably be close, but the difference between 5th and 1st on ASPHALT is being better than close. Stand back and look at the car, the housing is to close to the cross member, if there is an error it will be huge when stretched the length of the chassis, and after racing a car multiple times they all move and twist differently. If you plumb bob the car to the cross member, double check yourself by the following method. Remove the front clip(fenders, hood, grill). Find the point where the shock towers rise from the frame rails. Measure forward on top of the frame rail to within an inch of the bumper and mark it, do the same to the other side. Clamp your 60 inch bar across the front of the car on top of the frame rails on your marks. measure back to the rear wheels. (you can use the wheel base gauge to help you do this). You will say how do i know if the clip is straight? You may not, but if the clip isnt straight, then squaring to the rear cross member is that much worse. This is easy, takes simple tools and will give you alot of info. This car needs to be AS square as it can be, you need the rear square with the front area of the chassis.
Dennis Knox
Buckyey Legends
330-310-9212