Would the 4.7 liter from my 1999 Jeep Grand Cherokee fit in an A body?

KEEP THE SLANT SIX IN IT! With proper care, you'll never have a problem with it. If power is what you're after, grab a 318 at least, or a 360. Less work to drop them in, and less headaches later. Rustyratrod is right. I strongly advise against the 4.7, sorry