I think the top heavy thing is all relative. If you are used to driving pick ups, they will seem top heavy, especially the 2nd and 3rd generations. However having owned and wheeled both a 1st and 2nd gen 4runner (still own and built the 1st gen) as well as spending serious time behind the wheel of my parent's 3rd gen when I was younger, in my opinion, the extra weight up top is not really that important. My third gen extra cab seems "light" to me because I am so used to having more weight in the back.
That said, they do have a lot of windows and the interiors are prone to rattling over the years. They will not do wheelies going uphill even lifted, that is just silly. If you get the 1st gen you can take the top off in the summer if the extra 200 pounds is really that big of an issue for you.
