Car/Marine Radio Case for various sizes, don't have all kinds of radios so can't say if it will fit very deep radios

This design uses 4mm connectors for speakers, XT60 for power and a hatch in the back for all other connections from behind the radio

The center peg has to be screwed to the back of the radio, you can print the case first, put the radio you have into it and measure with caliper from the back of the case to the back of the radio inside, from here you can chose the peg you need or one that is longer, cut longer peg down in slicer (stop print after height) to fit your radio.
When you have the right peg length then screw it to the radio and lower radio in case, here you can glue it in when it is in place.

60mm Fan can be attached to a DC-DC buck step-down converter that is attached to "antenna power" from the radio, this turns on the fan when radio is on, set the DC-DC to a low voltage so fan spins slowly, fan is just needed to keep the case from becoming a heat box, make sure that the low setting you set the fan to is not to low so it wont start when power is applied.
Fan gasket is just to decrease sound further, try without first.
I use this fan, really quiet and cheap
https://www.tme.eu/dk/en/details/ha60151v4-a99-a/dc12v-fans/sunon/ha60151v4-1000u-a99/

Work in progress, will update with pictures in time