Found out today these are obsolete part and seems no one has a new one , They were 1600 list price ,and have only found 1 used one in Tenn. And they dont know condition of it. have a local spring shop trying to find material to fab one. So still looking .they are 5in wide 2 5/8 thick and 51 1/2 long . and weigh 140lbs .
Try the dismantled machines list:
http://www.machinerytrader.com/list/dismantledsearch.aspx?ETID=3&Manu=CATERPILLAR&Mdltxt=D4D&mdlx=exact
There is a spring company in RI that can probably make that for you. They have made special springs for me in the past .
I found a eqaulizer spring at Blount Equip in Hoboken Ga. 400. and 96 shipping and in like new condition . The old cat should sit up nice and staright now. Thanks everyone.