The minimum test voltage for 600V rated motors is 1000V, 250V rated motors test voltage is 500V.
A PI test is typically only done on motors >250 hp, a DAR test is done on smaller motors.
The minimum IR readings depend on the type and vintage of the motor and are corrected to 40 degrees celcius.
IR (1 minute)= kV+1 for most windings made prior to 1970 and all field windings.
(Example 480V motor = .48 + 1 = 1.48 Meg
IR (1 minute)= 100 Meg for most DC armature and AC windings built after 1970 (Form wound coils)
IR (1 minute) = 5 Meg for most machines and random wound stator coils and form wound coils rated below 1kV.
It sounds like the last would apply for your motor, take a reading (at 1000V) at 30 seconds and 60 seconds, your DAR should be greater than 1.0.
This info is from ANSI/IEEE standard 43 for motor testing.
