Optiplex 7050 Tower upgraded PSU options

There is no psu that fits because these "tower" units are actually sub compact.  They are Physically smaller than standard Tower or Mini Tower.

Making your own adapter is not easy and a standard psu must sit outside the case.  Moddiy makes one for 8 pin but I'm not sure about 6 pin.

http://www.moddiy.com/products/Dell-OptiPlex-3020-PSU-Main-Power-24%252dPin-to-8%252dPin-Adapter-Cab...

7050 tower PSU is TINY

May I know how you dealt with the external PSU in the picture? I just bought a new RX 580 and an external 500w GPU to power it, but the PSU won't power up unless the 20/24 pin connector is connected, but the OptiPlex 7050 Tower doesn't have a 20/24 pin connector on the motherboard! do you think one of these adapters can help (Links below)? I have also made a Reddit post describing my problem in more detail.

Reddit post: https://www.reddit.com/r/buildapc/comments/cgcewe/power_supply_help/

The two adapters: https://www.amazon.com/COMeap-Power-Adapter-Workstation-12-inch/dp/B06XW7RWNH and https://www.amazon.com/WYMECT-24-Pin-6-Pin-Adapter-Workstation/dp/B07P81LB2K/ref=pd_cp_147_1?pd_rd_w=P1z97&pf_rd_p=ef4dc990-a9ca-4945-ae0b-f8d549198ed6&pf_rd_r=8CSBYCZV18KXCN7RPHVV&pd_rd_r=2c35d30f-826b-45a8-8ef3-e224c51bd280&pd_rd_wg=xN9Ea&pd_rd_i=B07P81LB2K&psc=1&refRID=8CSBYCZV18KXCN7RPHVV

https://www.moddiy.com/products/Dell-OptiPlex-3040-3050-3060-Main-Power-24-Pin-to-6-Pin-Adapter-Cable.html

Regarding the Optiplex 7050 Mini Tower: Is there an option to install a conventional FULL Sized HD as the MAIN Mother Drive, (getting away from the chip-style SSD)?

Thanx