Dell PE 1950 II - Swap motherboard for something else?

Hello,

I have a Dell PE 1950 II and i've upgraded it as much as I can.  But I have some DDR3 ram and two Intel Xeon E5 2650's that I would like to use in my dell.

My Question is, would another Dell motherboard, say R620 or R720 motherboard fit into the chassis of my 1u 1950?

Most parts look the same, but i'm not sure if anyone has done such a mod, or if its even possible. 

Thanks for your time.