1934 Ford flathead fuel push rod

[Cmspencer]

Hey folks I’m working on a 1934 Ford BB truck project with a 21 stud flathead.

I’ve run into some confusion regarding the correct push rod length to use for the mechanical fuel pump. My engine is a 1934 21 stud flathead with what I assume is an original style aluminum intake manifold. Many sources I read through call for the 7.87 inch push rod for an aluminum intake. However when I installed the 7.87” push rod, it appears there is not enough travel for the push rod to actuate the pump lever. I had a spare 8.87” push rod that I tried and it looks like the proper length to actuate the fuel pump.

The rear of my intake manifold measures approx. 2.5” tall. I have included a photos of the intake manifold with the 7.87” and the 8.87” push rod at full lift.

I’m guessing that I need the 8.87” push rod, but that’s a guess. But then why do all the catalogs including the green bible call for a 7.87” push rod? Any help is greatly appreciated! (Newbie here so I apologize if this topic has been covered)