Dual quad geometry question

[55Brodie]

I have two Edelbrock 500cfm carburetors on an Offy intake and am using Show Cars reproduction progressive linkage. Can anyone share the dimension I need to drill the front carb arm so this linkage will function correctly?

Thanks in advance,
Brodie

 

[MRHP]

I use straight linkage and the throttle response is great. When I was using progressive linkage, motor was lazy down low. People use both, but I prefer straight. There are 2 sets of holes on the throttle arms. Use the upper one on the rear carb, and the lower one on the front carb with progressive linkage. You should not have to do any drilling.

 

[55Brodie]

Impossible to get WOT on the front carb using the factory lower hole. I just may go the straight linkage route and be done with it.
Thanks HP.