The 351C shares it's bellhousing pattern with the Windsors so the swap is straight forward. I did the swap in a '71 Mustang which is the same basic vehicle as your Cougar. An FMX cross-member can be made to work with minor slotting and grinding or custom cross-members are available. Details of my swap are at:
http://www.mustangsandmore.com/ubb/DanJonesC4AODswap.html
Dan Jones
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