Based on the info above :-
The stock spring is 75lbs/inch and about 4" long
The McMaster Carr spring # 9657k142 is 39lbs/inch but only 3-1/2" long.
The deficiency in length is a problem?
If so, check McMaster Carr #9657K136.
This is slightly larger diameter(1.25" vs 1")
It is 57 lbs vs 39 (or 75lbs.for OEM)
Fully compressed it is longer than the short spring 2.81" vs 2.31" Is that 1/2" a problem?
You can buy just one spring in # 9657k136
or this?
http://www.ebay.com/itm/131476133178?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
http://www.ebay.com/itm/15-16-O-D-X-4-X-0-148-Compression-Springs-Pack-of-2-/331396093635?pt=LH_DefaultDomain_0&hash=item4d28bf16c3