Hi miangun
I think there is no provision in API 676 for increase allowable like API 610. You still can talk to vendor for more allowable.
Gear pump allowable is less than API 610.
Gear pump I have worked with is generally one pump connected to one tank, not like 3 or more connected in parallel & with operating /stand by situation which generally create more problem in nozzle load for centrifugal pumps.
Check your situation, if only one pump in each stress system I think still it is manageable.

Regards
Habib