Combo advise needed!!

I've got a mild 440/727 with 3.73 ratio on 28"tres in a 69 cuda.
It cruises fine at 100kph(62mph) at 2600rpm.
At the strip on 28" slicks the standard convertor shows though.
3wks ago ran a 12.6@105 with a 1.818 60' weighing 3432lb.