Another Q about gears

I have a question about how the gears in the third member would affect the
running of the engine?
The build is a
383 cid + .040
Square decked , pistons .022 down in the hole, steel shim gasket
915 heads with bigger valves
KB dished pistons
According to my calculation this would give a 10.2:1 in static CR.
MP purple cam 284/484
Eddie RPM intake
Eddie 750 carb
Eagle rods
4-speed tranny
Centerforce dual friction clutch

I´m running NGK XR5 sparkplugs, Is this a wise choice?

Now for the question, I´ve got a 2,76 in the rear. I know it´s not to any advantage with this gear, but would it be to any disadvantage making the car to run worse or.... on low rpm:s ?
Many thanks in advance
Lenny