We rebuilt a '69 GTX 440 to stock specs,except used a 484 Mopar cam.Stock Carter AVS carb,iron intake and exhaust manifolds,906 heads unported-stock valves,only a .030 overbore.2-1/2 exhaust through Dynomax turbo mufflers.Auto 727 with a custom converter,mild stall.Initially it ran the stock 3.23 gear,then 4.10 gear.The GTX ran a 13.9 with the 4.10 gear,in drive shifts at 6200 RPM,never ran it with the 3.23.Tires are BFG 295/50/15's on 10" Weld wheels.The car has A/C and a choppy idle,but ok with the air on.It runs good with the 4.10's,but I always wanted to try it with a 3.55,the 3.23 gave it awesome top end and highway passing power though.I have tuned many stock or near stock 440's and think a 3.55 gear is perfect for an all around driver.The cam as installed may be your low end problem,you could try to advance the cam timing by 4*.BTW the 484 cam in the GTX will shred the tires!(I may have the gears backwards for the dragstip time,it may have been with the 3.23's)I'll check,it is a friends car,and the times were in the early '90's.
RT