To run? it doesn't need all that .It is necessary if you want any of the 110ft lbs of torque that it offers. That manifold design is very common... seems like they found the perfect runner length for torque and fuel economy for 1.8-2.0L sohc engines. Even the early 80's and late 70's BMW 1.8 and 2.0 engines used the same design... they just had more room being RWD so it sticks straight out instead of making a 90* bend over the starter.
You could just stick a pair of carbs or individual throttle bodies on it... custom adapters not included. I have dual carbs on my BMW, manifold length is about 4" and the carbs add another 3-4"? Low end power is nothing... but the engine I have is built for 7500+ RPM (Camshaft itself makes maximum power over 7500rpm) . It is also a 2.0 sohc.
The SPI... designed for torque (I suspect). Top end power is nothing. Cam is definitely designed for a low-mid range RPM. You would be very disappointed with a short runner manifold.
In other news though... that sucks. I've never had trouble with doing the starter with everything installed. Except for the bracket... that had to move.