EDIT: 8-17-16 : Here's a new guide specifically for the UEFI installation of El Capitan on the Elite 8300/3770 system from HP.
http://tonymacx86.com/threads/pastrychefs-testing-machine-hp-elite-8300-sff-i7-3770-gt-630.199712/
This guide uses a low profile GT630 GPU and not the integrated graphics (HD4000)
Directions for the HD4000 installation will be added later on. You would use either a DP to DP cable
or a DP to HDMI cable to use the HD 4000 integrated...
SFF HP Elite 8300 W/ Core I7-3770
http://tonymacx86.com/threads/pastrychefs-testing-machine-hp-elite-8300-sff-i7-3770-gt-630.199712/
This guide uses a low profile GT630 GPU and not the integrated graphics (HD4000)
Directions for the HD4000 installation will be added later on. You would use either a DP to DP cable
or a DP to HDMI cable to use the HD 4000 integrated...
SFF HP Elite 8300 W/ Core I7-3770