Update:
There is no E terminal in the 304 set. You can use the G GND terminal instead if you remove the yellow line cord wire. (This is just a convenient place to tie together the slate and slate-red ringer wires.)
I have an April, 1939 304 here that was rewired in the field for single party lines. The circuit is almost the same as the one above except the green line cord wire, green-red hookswich wire and the yellow condenser wire are moved from L2 on the terminal block to RR on the 101B induction coil.
This means that only one side of the line is now opened by the hookswitch, but this is OK.
Then the L2 terminal is available instead of the "E (354)/ GND (304)" shown in the TCI diagram, and the two extra ringer wires are connected to the L2 terminal (no other wires on that terminal). Then the GND terminal in the rewired 304 can keep the yellow line cord wire by itself.
The reason this was done this way rather than the way shown in the TCI was so that the ringer could be connected to the yellow wire for flat rate party lines.
Most 302s you see will have either the red or black ringer wire on GND, connected to the yellow line cord wire. Then you have to connect the red and yellow or the green and yellow together at the wall. Hardwired 500s also come with the black ringer wire usally on G.
If you are using a half-modular cord (modular on one end and spades on the other), in a 302 you would connect the red ringer wire to L1 of the induction coil, black ringer wire to K, slate condenser wire to K, and yellow condenser wire to L2/Y. On the 500, move the black ringer wire from G to L1.