Turbo Cartridge Replacement

[1983/300CD]

Does anyone know exactly how to take the turbo apart in order to replace the middle section (cartridge)?

There are 6 bolts at "A",
4 bolts at "B",
and 6 more bolts at "C".

Removing the 6 "C" bolts exposes the compressor blades. I'm assuming this is all I need to take off the front.

Removing the 4 "B" bolts does nothing. The turbo center section now spins, but will not separate.

Only 4 of the 6 "A" bolts can be removed because there is not enough clearance to remove the last two. (You can see in the picture that the top bolt is too tight.) There has to be some trick here that I don't know about. But in any case, when the "A" bolts are loosened, it doesn't help anything. It doesn't feel like it is going to come apart.

I would rather replace the cartridge than send it in to be rebuilt. Any suggestions?