The early springs were approx. 49.250", had a true arch of 5.875" and had eyes that were 
.8750" on both ends. The 58 and later springs had a larger front eye ( 1.500")  and the 
locating hole was approx 20.250" from the center of the front eye and had a true arch of 4".
 They were 51.750" long. Now all these dimensions are + or - .250" since the true arch 
will dictate the length. 

Alan (SDC FORUM) Nov 2011