I wasn't clear... I meant to ask if you WANTED to go to quad shocks, is there a lower mount for the second shock if your truck came with singles from the factory?

 

I think the P/N's are the same for 4x4 and 4x2 single shock option.

<style type="text/css"><!-- br {mso-data-placement:same-cell;} --></style><table dir="ltr" style="table-layout:fixed;font-size:13px;font-family:arial,sans,sans-serif;" cellpadding="0" cellspacing="0"><colgroup><col width="207"><col width="105"></colgroup><tbody><tr style="height:17px;"><td style="padding:0px 3px 0px 3px;vertical-align:bottom;color:#000000;text-align:left;direction:ltr;border-right:1px solid #ccc;border-bottom:1px solid #ccc;border-top:1px solid #ccc;border-left:1px solid #ccc;">Right Spring Tower</td><td style="padding:0px 3px 0px 3px;vertical-align:bottom;color:#000000;text-align:left;direction:ltr;border-right:1px solid #ccc;border-bottom:1px solid #ccc;border-top:1px solid #ccc;">EOTZ-5A306-E</td></tr><tr style="height:17px;"><td style="padding:0px 3px 0px 3px;vertical-align:bottom;color:#000000;text-align:left;direction:ltr;border-right:1px solid #ccc;border-bottom:1px solid #ccc;border-left:1px solid #ccc;">Left Spring Tower</td><td style="padding:0px 3px 0px 3px;vertical-align:bottom;color:#000000;text-align:left;direction:ltr;border-right:1px solid #ccc;border-bottom:1px solid #ccc;">E2TZ-5A306-J</td></tr></tbody></table>(These are the ones that I used on my 4x2 F150, ordered from tascaparts.com)
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The stud for the forward shock on each side is already there on my truck which has single shock towers, should be all you need is a nut.