We will need more info, the mower model number, the Kawasaki engine model number... what vanguard you are looking at too.
Most wiring systems can be diced and spliced together provided you know what you're doing... and with the help of experts on here.
The main things when repowering equipment.
Never go less horsepower or torque then the original engine
Make sure the crankshaft is the same length and diameter
you may also have to fabricate, or buy a new muffler.
Most engine mounting to frame patterns are standardized for certain size engines.