Not to confuse matters, but I did a small amount of research when I bought mine. The bottom line is that the TW's get more inaccurate as you move toward their extremes. You basically cannot use the same wrench for head bolts as for the acorn nuts that hold the cam cover on.
With that said, I would get a 0-50 ft/lb in 3/8 drive and a 0-150 in 1/2 drive. I personally like the clickers for repetitive tightening and the dial type for onesy-twosey.
So I bought a 1/2" 150 Craftsman clicker and found a 0-50 Snap-on dial type on e-bay. The latter comes up frequently because places like Pratt & Whitney only use them for a defined number of "pulls."