I run a '70 Challenger with aftermarket UCA's. Mine are Firm Feel. The aftermarket UCA's can help achieve better alignment settings: combination of more positive caster and negative camber. This works well with radial tires and especially if you want improved handling. Custom alignment specs required to get the benefit.

I don't think the LCA's do much for alignment. OE LCA's can be plated to handle higher loads (see Firm Feel) or just left alone. For street driving with stock sway bar (if fitted) I really don't think an aftermarket LCA will help much unless yours are shot and otherwise need replaced. If you are pushing sway bar size and T bars beefing the LCA in some fashion may help.