It goes V1, V2, V3(is the loop send/return), V4 is the PI. The reverb is from a spring tank, there is no tube used for it. The pre-gain is from the 2 halfs of V1 & v2. Up to 4 stages.
V1 is under the metal shield. V4 is right next to the power tubes.
This amp has 5 gain stages. Uses V3 as 5th and reverb return. Effects and Reverb are not tube driven. (op-amp)