What GPU’s will fit?

Hi, I’ve been given this neat little Dell Vostro 3470 already with an SSD as the corporation who initially owned it wanted rid of it due to the lack of RAM (4GB…. Planned obsolescence if you ask me)

Now I intend on keeping this as my main computer, I don’t often use a computer but when I do it’s heavy workstation, zoom meeting, 100 tabs open on google chrome across 3 screens workloads.

The current FX8320 @3.72ghz, GTX960, 24GB build which I initially built at the end of 2015, it’s now really showing its age to be honest. I’ve been looking to upgrade on a budget for the past 2 years but haven’t had a great opportunity.

I intend on upgrading the CPU in the Dell to the i7 8700 (appears to be compatible?) throw in 16GB of ram…. But NOW I’m completely stuck, I can not find a suitable GPU which will physically fit inside this PC, I know they exist I have seen small form factor gaming builds but I can not for the life of me find any decent GPU’s for a small form factor, just one that matches the performance of the 960 at least with 3 DVI or HDMi outputs (or a tossup of both)

I’m asking for the expert advice here! Please!