Will a 1993 Lincoln mark viii v8 4.6 engine fit 1994 mustang?

No, a 1993 Lincoln Mark VIII 4.6L V8 will not fit directly into a 1994 Mustang without significant modifications. While both are Ford products and use a similar engine family, the mounting points, accessories, and overall engine bay dimensions are different enough to make a direct swap impractical. You'd be looking at major fabrication work to make it fit.