What differential type do you have, (LSD, locker, open etc.) and how much power do you have?

Sorry Guys.Forgot to mention it has a limited slip Banjo diff with moderately improved torque(6 cyl.slightly bigger head,20/60 cam, 2 barrel holley,single exhaust extractors) .Yes it does have rebound and compression damping.

As WBute and Castellan said, there a lots of things that could be an issue here.
What you describe is what LSDs tend to do - reduce inside unladen wheels spinning, and drive the outer harder than an open diff. At least you don't have a Detroit locker, or worse a spool. I wonder if you've done much driving of an LSD car in this kind of situation? They definitely behave differently to an open diff.

I suggest you check the basics first, before getting too much into more complex things.
That said, first I'd check the condition of the LSD and measure the breakaway torque. Its fairly simple really. Find some way of turning the rear wheel with a torque wrench (not via a wheel nut!) perhaps with a piece of flat steel wedged between the wheel nuts with a single large nut welded to the centre.
Chock the wheels, take the handbrake off, take the car out of gear, jack up one of the rears and see how much torque it takes to rotate the rear wheel. If you have a fairly standard banjo LSD you would expect 50 ft-lbs or more. Check it on both rears, and they should be about the same. If not - get the diff fixed!
Next, check the rear spring to diff insulator pads. They do wear out and give you all sorts of odd rear end steer behaviour, particularly under power, as the diff can move forward and back by sliding along the leaf spring under power and braking. You can normally see if it has been moving by shiny surfaces on the rear springs. Also check if you have the right number and thickness of steel spacer plates between the diff spring mount and the spring clamp plate. Also check that you have the appropriate thickness rubber insulator pad. There are two different thicknesses available for HT, depending on the model.
As you have different rear springs to standard, and I don't know what flavour of HT you have I cannot help you with specifics here.
Next, check the front and rear wheel alignment at a front end specialist. If the front springs have been replaced with springs with a different ride height the camber and maybe castor will have changed.
The standard figures for HT, from memory, are 0-1 degree positive castor, 0-1 degree positive for camber and zero to 1/8" toe in at straight ahead.
I personally prefer about half a degree negative camber but this can be an issue if you have large tyres on the front.

You will note I said get the rear alignment checked as well, and some may think this is madness. The reason is to check if you have a bent banjo, which is not unheard of, and not always easy to find. It should be zero for everything if the diff is straight. Tell the alignment man why you want it checked, and if he is worth dealing with he will understand.

The setup you describe is difficult to comment on further without knowing the spring rates, but a rear bar on anything will be more likely to make it lift an inside rear wheel, and make it more tail happy, depending on the spring rates. I suspect that you want the rear dampers on full soft, and the same on both sides, (for bump and rebound if they are dual adjustable type) as a starting point

Sorting suspension is what most competition teams spend the most time on, and it isn't easy as there are many interacting adjustments. Usually it ends up as a compromise and in your case it depends on what you want to do with the car.

Hopefully that is of some assistance, and goes some way towards meeting your definition of "easily solved"

Some time ago I did a major upgrade from the original suspension setup.
I recall the car handled reasonably well.Then one day I replaced the shockers to Konis.Unfortunately I didn't keep a log of what I did.Also I didn't test the car to it's limits to see if the shocks needed adjustment(other things became a priority).I think I'll start with shock adjustment.You guys however have given me some great tips which I'll keep a record of.Thanks a lot.