The pump is held in by four bolts. The sneaky bolt in the DIY above is the hex/allen bolt (shown removed, it's the left most red circle in the second photo). Expect some coolant to spill out once you get the pump removed.
I'm grateful to have had a salvage yard M42 to practice on, as it will come in handy when I have to do it to my own M42.
Adios for now,
On Christ the solid Rock I stand, all other ground is sinking sand. (Edward Mote 1797-1874)