Hi Jason This will not be possible, I believe the io in the rear is slighty different, the power supply's for an R720 will not work with a R730, the backplane connectors, sas cables, power, usb and front panel connectors are all different and the fans are different also.  although they may physically connect together the pinouts are different so will not work or work correctly Dave
Hello! Is it possible to place a R730 motherboard into a R720 chassis? My R720 motherboard is faulty that I would like to replace it. I know that R730 uses E5 v3 CPU and DDR4. So that CPUs and RAMs have to be replaced together. However, I want to make sure other things are compatible, such as screws hold, front panel connector, power connector and fan connector. Any body know about this? Thanks. Jason Tsang (helping a seminary)  
R730 mother in R720 chassis