Re-worked the blocking out of S1 machinery for reactors, energiser and propulsion based on the latest model I posted a few days back
There are 3 M/AM Reactor cores which make up the M/AM Reactor (system). I blocked in the basic core elements (reactor core, Antimatter fuel pod, Matter fuel cylinders) in one of the nacelles to get a sense of the space taken, copied to the other nacelle and re-arranged the same parts in the Engineering hull. Interestingly, the parts fit the bottom hatches. The reactor is shaped like an over-armored warp reaction chamber from TNG turned on it's side
The M/AM energy conduit runs a similar path that the TMP Enterprise Warp Intermix shafts would run. There are also separate matter and antimatter fuel lines that run between the 3 fuel locations. I've included where a possible location could be for Scotty's fuel crawlway from "That Which Survives".
The lithium (and then later dilithium) energiser machinery is positioned to take the M/AM energy, do it's magic crystal amplification and pumps the power back out through the various power conduits/circuits. A feed branches off and back up to energiser units in the nacelles.
I took a best guess with the warp engines. The rear sphere is layed out to be retractable.