Question about HP ProDesk 400 G3 MT

I installed a Zotac GeForce GTX 750 Ti - 2GB for a customer.
It fits without having to unplug anything, and it works or having to install a stronger power supply.
But I wouldn't install much more than that, because, as Biancoblu said, a PC like this isn't meant for a huge upgrade. You don't buy a Fiat and then install a Porsche engine ;)

My ASUS GeForce GTX 1050 Ti STRIX O4G fits in, but the internal USB connector for the front ports on the mainboard is in the way. If you pull out this connector, an error message appears during the boot process, which you have to confirm with Enter. I could not eliminate this error. The graphics card you are aiming for is shorter and may fit without the USB connector problem.

Also note the power supply unit! The power supply of the HP PC offers 180W, but the graphics card needs 300W. This means buying a new power supply.

Such HP PCs are not intended for tuning.