On the Carter strip mechanical pumps, 1/4" NPT is the fitting thread size on the pump's inlet and outlet. This is NOT a restriction if you're running 3/8" fuel line. They are not 1/4" diameter ports on the pump. It's actually larger than 3/8" diameter hose.

A Carter mechanical strip pump (the 8.5 psi version) will feed your motor. I ran one for years on a 440 in my 'cuda that was running 11.40s at 117 mph. I "upgraded" to a Holley blue pump w/ -8 (1/2") fuel line and didn't see any difference in performance. CHIP