Diff ratio help

I have 3.0 gears on my 426 barracuda (8.8 ford diff, 500hp) and runs nice off the line and in the highway at 130-140kph speeds with the stock 4 speed manual. I do not race it in quarter mile dough, its a daily driver. Its below 3000 rpm at 140kph so that is good for me. I have 275/40?/17 rear tires.

I would recommend for your case to enter the transmission gear ratios you have, define what rpms you would like in the highest gear at yoyr highway cosntant cruising speed and play with the ratios availablw for your diff and see what you like best.

Take care,