Itmalic, The issue is that the VV3F2 board is a newer version (Version 6) than the KCKR5 (Version 2). So any other hardware based off that difference can cause issues. 
I have a R620 with a bad iDrac enterprise and it looks like a motherboard replacement is the only solution.  The label on the motherboard shows that it is a 0VV3F2.  Will a KCKR5 be a suitable replacement for it?      
R620 0VV3F2 Motherboard replacement