Andy's book gives an easy and simple answer for it all.

Another easy answer is simply set your car up to fall on the neutral handling line as shown below from the Mike Martin book, Mopar Suspensions.



Of course, getting front weight percentage is easy. Its all the calculations that go into figuring out roll couple front and rear that make it tricky. Martin's book gives info on how to do this, as do the other books listed above and the Mopar Chassis and Oval Track books also have info on it. Where it gets tricky is you can't just plug in rates. You have to find motion ratios of the sway bars front and rear and rear springs. T-bars are 1:1, so that part is easy. Once you have all this, then yes, its possible to set up a formula that show you where your car falls and then you can target the percentages on the chart above. I created one for my Challenger so I can see what changes may do to it, but I also have a configuration on my car that is different than stock using many non stock components, so it doesn't easily translate to other vehicles. I also set my calculator up to back into required leaf spring rates as these are the easiest part to customize. There are only so many t-bar and sway bar pieces out there, so we are limited on how wide a range of front end set ups we can get, whereas leaf spring can more readily be modified to match the front system.