Need help with 60's

[JG33RD]

Having really crap 60's I thought I might be able to get somewhere with carb tuning, however it seems my carb is not the problem, deatails are XB sedan approx 3200lb full manual c4 5000 stall (not built for this car) 3.7 rear 26" M/T drag can only manage about 2000rpm off the line without creeping out of stage, flashes to around 4500 (shed test only lol) shockes are competition engineering front and rear set 90/10 front and 50/50 rear, no noticeable wheelspin and can only manage a best of 1.9 flat with approx 500fwhp and 426ftlb. Any help appreciated.