The Cline regulator would have to be installed on each engine. It needs to be installed an inch from the carb... per the instructions. I've had a two and a half inch length of fuel line connected to one once just because I didn't have room to mount it closer and it worked fine. They sense vacuum from the carb and release fuel pressure to feed it. Also I was using the oscillating pump, I swear by them on 4 strokes with funky tank placement.

Those oscillating pumps put out an impressive amount of flow and pressure, even when adjusted down quite a bit. Put a cline on each one, a single tank and a single pump, run a bench test and adjust the pump till your happy!

I'm starting to plan my first twin project... and after that a four engined rig... hopefully sooner rather than later!