My personal favorite for sound is a real oldie. The inline 6-71 (Old Looks) and following close, the 6V-71 (New Looks).
For power, the 8V-71.
Being in a hilly area, I was pretty much raised on the 6 cyliner 71's screaming up the hills around here. The 92 series engines seem to lack the same "charm" when climbing hills.
I know others will disagree but I personally feel the 8V-71's were better by far with pulling hills than the 6V-92, especially the ones using the V-730 transmission. They were actually quieter than the 6 cylinder engines since they didn't need to fully rev out to get to the top.
A lot of what I've heard about lack of power has to do with the transmission more than with the engine. A 6V-71 engine using the old 2-speed hydraulic transmission has far less power than the same 6V-71 connected up to a 3-speed hydraulic or V-730 transmission. A 6V-71 with a V-730 transmission can easily outrun an 8V-71 that's using an older 2-speed.
Axle ratios also play an important part in speed and power. An axle geared for highway speeds will move the bus faster than a rear end geared for city driving.
RDChilds