i know there is a company that makes all the mounts and such to bolt in a mustang 302 and trany. seen mini truckin do an artical on the install you just need to do some searching

 

If you're going to all that trouble anyway, why not go diesel? The cummins 4bt is a common engine that should be able to give 105-125 horse and 290-375 lb/ft of torque depending on the setup. All that torque, longevity of a diesel, and 25-30 mpg! You could even start making your own bio-diesel and run that engine for around $0.70 a gallon.