on my 65 coupe, my dad replaced the rear frame rails and trunk crossmember. Its been a while since i really looked at the job he did and now that i have i noticed that the crossmember is not centered, now the frame rails are 43 inches apart as it calls for BUT one side from rail to the end of the CM is 31/4 or so and the other side is almost 4 inches. DOES THIS HAVE TO BE PERFECT?