Google Maps (http://maps.google.co.uk/?ie=UTF8&ll=39.754333,-84.160144&spn=0.012719,0.036049&t=k&z=16) still shows the old layout on the aerial images although the mapping and streetview shows the new layout.
Does anyone know what was originally intended? It was obviously intended to be much more than a link to surrounding streets. Northbound was probably going to extend to route 4 to provided an inner belt around the CBD. I have no idea where it was meant to head south. The most intriguing aspect of the old layout were the 2-lane ramps from W<>S with their smooth curvature. Compared to the other ramps the layout of these suggests this was going to be the main traffic flow.
Some time back, I found a webpage with some early planning maps. The 1950s-era proposals for the "Southeast Expressway" were for the highway to extend well to the south...at least as far as Centerville...paralleling OH 48 about a mile to the east. At one point, there was an attempt to use the proposed highway as the routing for I-675, but this fell through early on. By 1965, the highway's length was significantly cut, only extending as far south as Wilmington Ave (just east of Shroyer Rd).
To the north, it would have tied into OH 4 at Stanley Ave, and then use Stanley Ave to connect to I-75. Early maps suggest Stanley Ave would have become freeway-grade, but the 1965 map suggests it would have remained at-grade.
Maybe Sherman is lurking and will respond to this thread. Urbanohio.com was where I saw someone's research on that interchange.
The aerials on Bing are post-reconstruction.
I've worked on some maps of Dayton suburbs and I'm always struck by how US 35 was rebuilt through downtown mostly as-is with all the left-hand entrances and exits.
I mean c'mon!