Proportioning (combination) Valves Differences?

Is there a big difference between proportioning valves pop rate for the drums, and the meter for the front disk? I know the proportioning only works in a panic brake scenario, but what about the front metering?

The reason I ask is the local Napa has a combination valve for a Grumman LLV. If I adapted this part to my Jeep, is the metering going to be wrong that it will not work correctly? If so, should most any combination valve work as long as it is a disk/drum unit?

As a side note, what a bitch to get the combo valve out from under the Jeep. I am going to re-plumb the brakes and put the valve under the MC. Absolutely so little room to get it out, don't want to even try putting it back in the same spot.