There's few ways to do this.
You can take advantage of #copy.bottom-section (which is the Post-nav area) and use css to move it around and at the same time move the margin of #exhibit
#copy.bottom-section p { width: 350px; }
#copy.bottom-section {
width: 350px;
bottom: 0;
left: 0;
margin: 0;
padding: 0 0 0 40px;
position: absolute !important;
text-align: left;
top: 140px;
z-index: 100;
}
#exhibit { margin-left: 400px; }
Of course this is a layout in which the second panel stays the same thoughout the site.
The alternative and dynamic way to do this is to customize the over and over format to have the layout that you're after... Or whichever format you want.
The Horizontal format for example is exactly like you want but images scroll sideways.