You can refer below link for details on GPU supported riser combination and slots [URL] Below link have details on GPU card installation guidelines  [URL] 
Hi everyone, I am trying to upgrade my dell powerdge R740 to make it work with TESLA T4 card. Nobody at dell customer service nor dell technical support is able to assist me, so I am quite desperate. We plugged the TESLA T4 on a riser1 card, the tesla is visible in windows server 2019 with licenced grid rtx drivers but our 3D softwares are not using the card so performances are awfull. I suspecthe riser card to be the wrong one asit seems to be a X8 pci device or maybe something  wrong in the hardware config but I am n ot sure. Can someone help me ? parft number for the riser card is: 330-BBGZ   Thanks    
TESLA T4 on poweredge R740