For anyone interested, virtually everything inside the E-100 hull is from a King Tiger. Engine, radio, batteries, driveshaft, seat. At the rear, there are two fuel tanks at either side of the engine bay, these are a different shape.
In real life, the prototype engine is a donated HL-230 from a King Tiger, for trials this put out 700BHP. Put into service the engine was going to be fuel injected and raised to 900BHP (HL-234). The plans to upgrade to HL-235 were not feasible as they would've required moving the firewall forward. The HL-235 is a supercharged King Tiger engine, it produced 1,200 BHP. I believe only the French put one of these to use in 1946, having captured components in Germany.
There were plans for a StuG E-100, but these were scrapped. The tank hull was to be the only example of the chassis. The 'Krupp' turret, seen in World of Tanks and Amusing Hobby's version of the tank never existed, only in blueprints. The author Ken Estes has postulated that this turret would never have passed troop trials because of the gun layout.
It's likely one of the empty Maus turrets at Essen would've been paired with the E-100 hull, as was originally intended. In this sense, in my opinion the most realistic 1/35 release of the tank is the Dragon models version (and in gaming, the War Thunder version).
Creating a full interior for an E-100 would require the innards of both a 1/35 Maus and King Tiger.