Does anybody know where to get specifications for a rotax 435 motor. And where to get coils for it.

What year, what model of sled are you referring to?

Here are some specs from a 1973 TNT 440 (435 Rotax) is that helps....

Type: Twin Cylinder Rotax 435
Location: Center Mounted
Displacement: 436.6cc
Bore: 67.5mm
Stroke: 61mm
Horsepower: 42hp
Carburetion: 1 x HD109A
Sprocket Ratio: 18:34
Ignition System: Magneto
Engine Cooling: Fan-cooled
Exhaust System: Tuned Exhaust