why don't I see down-draft fuel distributors on up-draft metering plates?

[ArsenicPants]

I'd like to use a Mercedes 8-pot fuel distributor, but I also want to keep the standard up-draft VW metering plate
I understand the downdraft plates move the plunger in the dizzy upwards, while the updraft ones move the plunger downwards, but if i swap the plunger from one to the other, would it work the same way? the fuel galleys inside of the dizzy are in the same place vertically between the two, aren't they?

thanks

[WaterWheels]

I'd like to use a Mercedes 8-pot fuel distributor. . . I understand the downdraft plates move the plunger in the dizzy upwards, while the updraft ones move the plunger downwards . . .

Nope, they both move in the same manner to do the fuel delivery. The difference is the pivot point for the two. The updraught type have the pivot point at the end of the air sensor arm and the plunger rides in the middle (more or less). On the downdraught ones the pivot point is towards the middle of the air sensor arm and the plunger rides at the end (again more or less). So the movement of the air sensor still causes the plunger to move in the same direction.

As for wanting to use the Mercedes fuel distributor I guess that would be another topic.