Mallory 140 pressure question to Rochester

[Mr.Pontiac]

1967 gto car starts up at 7 psi, had it out today and at 90 mph fuel pressure drops to 3-1/2 psi, tank is sumped no.10 to pump and no.8 to carb. Seems i have big enough lines, sound normal??? Full tank of gas.
Running a Robb Mc fuel filter in no.10 area. Please forgive my posting here, looking for a answer, Thank You!

[omaha]

i remember "trying" to drive my 67 GTO at 90 mph. It tried to leave the ground! THat was a long time ago when I had that car. (to the car's defense, the bumper was missing at the time).
    Is this fuel filter one of the "pre-filter" types that go before the pump (to protect the pump). If not, there could be an issue with restriction but I am assuming it is the appropriate filter. Pre filter and post filter are different. what other filters are you using?