The TR4 has what might be described as a harsh ride, at least by today's standards. Although uprated front sprigs may very well affect the handling, I doubt they will greatly improve the ride. My TR3 still has it's original springs, so I'm not the one to give advice on the uprated or the competition springs but I would say that renewing the suspension, shocks and steering, with new well balanced tires, if you haven't already done that, will have a greater positive effect on the ride. Everything else done, new springs might be a final step. Hopefully someone experienced will make a recommendation for springs.
Tom