OK. I took delivery of the new amplifier boards, pre-amp, and speaker protection board a little while ago. Unfortunately they are slightly too big (or more the wrong shape) to fit in the original amp board locations.
So after a bit of jiggery-pokery, some serious hole cutting and hack saw action for the air vents, and a bit of re drilling the inputs and screw holes, things are looking like they will line up and fit. Hopefully this is the last of the physical modification of the unit I need to do. Next comes the re-wiring phase of the project, which could get quite interesting.
The newly uploaded picture shows everything mocked up, trouble is I have lost my heat sink paste and my toothpaste started to taste funny. I just hope the two aren't connected. Anyway production will have to stop until a new tube arrives.
Oh and just for reference, those smoothing capacitors on the power supply board, are still charged after sitting for almost a month. Fortunately the case took the power out of them (and not the back of my hand).