My T100 has a similar setup in the front. I tried some poly bushings after my stock rubber ones were shot. I quickly replaced the poly bushings with stock rubber bushings because the poly bushings were way too stiff. My sister has a 99 4Runner limited and the front end is pretty bouncy. I would think that harder bushings would make the ride too rough. Just my thoughts.

97 T100, 32" BFG/AT, Warn hubs, stock height with Bilstein shocks, Optima battery