A motorplate is very convenient. It's a great place to mount things like the coil, vacuum pump, breather tank, alternator, etc. Much easier to unbolt than typical motor mounts...makes engine removal and installation much easier. Plus it frees up a bunch of room under the car when you get rid of the standard mounts and brackets on the K frame. MUCH better for header clearance...especially on a hemi.
It's probably stronger too now that you've tied it all in to the frame rails...acts as a stiffener b/t the front rails.