The 351 is part of the Windsor family, which is not 'modular'. It was designed long before the 4.6/5.4 family.
The horsepower varies, usually around 200 when used in a truck (where most fo them were found in the late 80's through late 90's).
The 95 Cobra R used a 351, but there were only a couple of hundred of thoses built.

It will fit in a 97 Cobra chassis, but not really worth the trouble as far as I am concerned. What is wrong with the cobra 4.6?