I mocked up a battery (lighter than a proper one and less risk of damage test fitting in awkward spaces).
This is becoming a game of tetris. Fuel pump, filters and pressure regulator (with gauge), fuses and relays, battery, fuel tank, extinguisher bottles, cup holder, ice box for inlet air (long shot it will have any effect), airbox and ducting for ITBs, inlet air NACA/ scoop ducting etc.
Dimensionally my mock up battery is just like the one in the catalogue but it won't hold a charge - what did I do wrong?
Pictured sitting on a chassis rail; this will not be its home. It will weigh around 15 lb - ideally I would like to move it forward under the seat for (slight) weight distribution benefits but that means more holes in the already crowded firewall (most of which will be occluded by the radiator tank). Current count is: shifter rod, throttle cable, clutch and brake line, some wiring from the instruments, chute cable, extinguisher cable times two and extinguisher hose for cockpit nozzles. If the ECU goes in the cockpit that's a large bundle of nerve fibres to pass back to the engine bay and a long wiring run for them too.
At this stage (avoiding the exhaust side of the engine) the battery could sit next to the gear box but that shifts the tank backwards as that is likely to sit in the space on the left of the gearbox (behind the scattershield) too.
The fuel weight being on the left of the vehicle will offset some of the weight of the engine top end canted to the right.