The engine is a 2002 Cat 3126E on a Spartan Summit chassis. The compressor is OEM by Cat. It does not have the unload connection to the governor. This is confirmed by the Spartan documentation.
The unload function appears to be provided by the dryer, a Bendix 1200. I have confirmed there are only 2 connections to the governor, one to the tanks and one to the dryer. This is not a optimal configuration. It means the compressor is continously pumping air only to have it discharged by the dryer.
Since this is a 'standard' compressor with the unload capability is it reasonable to simply add a connection between the governor ant the compressor?