Signature Lincoln Mercury:
(800) 876-3280
Ask for Steve or Bill
Check the 3L forum for FAQ's, and there's a good How-to on the NECO forums (forums.fastcougar.com).
You can swap in a 3L shortblock with minor modifications. Going with a full 3L with 3L heads requires some custom fab work to your fuel rail and EGR (at least for pre-98s)