Little update and further questions. Got the resistor replaced and both caps on the transformer board(C63 and C64), that's all good now.
Received replacement Murphy 3 ohm speaker from Phonosandradios(thanks!), plugged that in and we have sound. Volume though was still bit low so decided to tackle panel 6 which turned out to be a complete mess and it took me a little while to figure out what previous person working on this tried to do here. Lots of extra wires and wire leftovers were removed, single 50V/50uF hunts cap was replaced with two 16V/100uF(original 75uF caps missing entirely), while in there I've also replaced both carbon resistors as although they were within spec they looked like they were proper fried many times.
Switched the radio back on and we have proper volume, the initial crackling at LW made me jump
Had a look at both AC4/PENs and I think I've got one of them faulty as cathode voltage on one of them only goes up to approx 6.2V, the other is fine at 8V.
Two questions now.
1. Am I right thinking that this will need a replacement?
2. Are 16V/100uF caps ok to use instead of original 75uF or should I order the latter? I take it 16V is plenty enough?