Ok see here is the experimental file. I must warn you that 320x240 does not look good and weird scan lines which will probably make the converter look worse than better. For this reason I recommend using 480i60hz and the frame buffer 640 480 too.
But if you want to test here is the 320 240 settings, First SSH in then copy/paste 1 line at a time.
cd /emuelec/bin
wget https://gist.githubusercontent.com/Langerz82/c757f4404375a09efae9f84968ee997f/raw/8df418c85365314296d8f8816c9dfa753f4126c3/setres.sh
chmod +x /emuelec/bin/setres.sh
cp /usr/bin/emuelecRunEmu.sh /emuelec/bin
nano /emuelec/bin/emuelecRunEmu.sh
look for the line:
[ ! -z "$VIDEO_EMU" ] && $TBASH $SET_DISPLAY_SH $VIDEO_EMU $PLATFORM # set display
add just above it:
[[ -z $VIDEO_EMU ]] && VIDEO_EMU=$VIDEO
save and close.
Then add the following records to emuelec.conf with the command:
echo "ee_emu.framebuffer.640i60hz=320 240" >> /emuelec/configs/emuelec.conf
I think that should do it. But yeah, my recommendation is that you just settle with 480i60hz.