What haven't I thought of with this issue?

[ubtripn]

My truck has new inner/outer tie-rod ends, upper/lower ball joints, new drums and brakes, new inner/outer bearing / new shocks and new tires and rims along with a new stabilizer bar BUT....it still rides hard, the shocks are stiffer but when I hit a manhole cover that is a little deeper like 1-2 inches down-BAM! My 66 has none of these items replaced and it rides great. I cannot figure it out. The last thing I can think of replacing are the coils.

I have kept everything to the engineers original specs including tire size so I just don't know. What symptoms do bad springs cause? I can see these little triangle rubber bumpers on the a-arms as well but I am not sure what they do. Anyway, any ideas on how to get a smoother ride and less creaky ride. (I have lubed everything with a zerk.)

Truck drives straight with about 3/4 of an inch of play if that.

Thanks.