I was mostly looking at a somewhat standardized layout for a sci-fi air/space ship running Mach-Lorenz thrusters.

The reactor I understand would probably be a 2 to 5 meter cube, as I understand it, depending on the power output. There would be vacuum pumps for atmospheric operation--in space you'd just vent the reactor I think. For military purposes, it would probably be best to skip trying to scavenge helium--it's another doodad to mess with. For space operation, the cryo plant would include a reserve tank or two to keep the cooling system full.
I was thinking to use the "venetian blinds" converter to harvest power, with the converters in tubes connected to the main reactor. Problem is, I'm not finding much on how big the converters might be.
I'm thinking the tube for the "blinds" would be a few meters long at least. So, with a five meter reactor, and five meter converters, you'd have a fifteen meter box, with probably at least three decks in the compartment, and subdivided as needed for other requirements. Do you think you could fit everything in a cube like that?