The GE AK-2-50's interrupting rating depends on your system voltage and if they are equipped with direct-acting instantaneous overcurrent trip devices. Here's the breakdown.
System Voltage|Interrupting Rating w/ Instantaneous Trips
600 VAC |42,000A
480 VAC |50,000A
240 VAC...
dpc & Scotty are correct, although contactors are cheaper and are designed to endure "operational abuse" so to speak, I cant think of a contactor that could effectively support a 3500HP starter.
If it's the price that is shying you away from going with a breaker, consider remanufactured...