That is true but aircraft have rather strict center of gravity limitations so it cannot be a single big lump.
http://i.imgur.com/cxW1aMJ.jpg
Everything has to fit were the existing engine, exhaust, ballast weight, and fuel tank were and maintain the CG. There is about 160-180 lbs available for the entire power system.
This plane is ripe for conversion since it was designed for a larger gasoline engine and has a substantial amount of ballast mounted on the engine to get the CG in the right place. It has a very lightweight engine paired with a heavy steel exhaust and a ballast block that is about the same weight as the engine itself.
The higher voltage EMRAX motors would be a very good fit but a controller that can handle the high voltage is huge since they are designed for 100kw motors rather than the 30 kw peak needed.