manual steering coversion?

This is what I used. I've had it for about four years with no problems.

http://www.mustangsplus.com/Merchant2/merchant.mv?Screen=CTGY&Store_Code=MPFMP&Category_Code=adapter

If you just want to do the center link I'm not sure if that's all you will need. I don't know if a manual center link will work with power pitman arm, idler arms, etc. From looking in the Mustang Plus catalog they seem to be power/manual specific.
I'd look on ebay unless you want a new center link.

http://www.mustangsplus.com/Merchan...MPFMP&Product_Code=00602&Category_Code=center