New drag car

With your weight , you should be able to pull a 3.91 with no problems at all.
Calculate your mph vs. rpm and if you have more that 10 % slip your converter would be suspect.
I think the T/A converter would be a better choice too.......something in the 4000 range will put the motor in the meat of the torque curve better than a 3000 piece.
I'd calculate your slippage and maybe try a converter swap first if the Fairbanks is leaving something on the table.
A 4.10 isn't over geared by any stretch. Maybe a taller slick to drop finish line rpm ?
I won't make a guess about how high to spin it , but with light pistons 7000 is not unusual in a big block.