Ender 3 Pro MeanWell PSU fits perfectly under Y axis extrusion in the back.

You can print 1 or 2 front parts (to be put into central 4040 extrusion), I decided that one is enough for me.

To fix left and right part you will need 4pcs M5 screws (I used ISO7380 M5x10) and 2pcs M4x6 (I used ISO7380 M4x6)
There are 2 versions of the left parts with different power plug fixing screw holes diameter.

UPD 22.05.09 Fixed some minor flaws

UPD 22.10.25 Redid Front piece to be sturdier.
Added light version which is also easier to install - just roll it in. This piece is need to be tested though.