Probably not. The rear I/O is punched into the case. Also Dell uses a proprietary front I/O cable that they add and remove things from and change their secret pinouts.
I would look for an Optiplex 360 MB. At Userbenchmark.com I'm seeing them running Xeon E5450, and X5450 3GHz quad coes. They score just as fast as any Opti 780.
The X5450 is interesting since it's rated at 120W, so no 95W limit, and the E5450 is 80W so a little headroom for a software overclock (maybe, some Dells are more locked than others). GTX750TI was the best GPU. A 1050Ti would shake things up!
http://www.userbenchmark.com/System/Dell-OptiPlex-360/4042#Compatibility
These or the Q9650 I'm not seeing there for some reason, and the 1050 would give about 40% ranking in CPU and GPU.