C60 basics - school me, please?

[yossarian19]

So, I'm about 85 percent done with my '57 3200 Vortec 4.8 / 4L60E project. It drives, so I'm already thinking about my next project.
For reasons I can't begin to guess at, I think I may need a C60 or earlier 2-ton (ton and a half? and a quarter?) truck. A car hauler, perhaps? Tow truck? I don't know why I need this, but I think I really do. It's an illness.
I'd been thinking right off the bat "Hey, this is a great truck for an 8.1 / Allison 1000 / Rockwell axle swap" followed by "Nah, 14 bolt FF..."
But then I read that they have dual-speed rear axles & that they came with 6 cylinder engines under 300 ci.
So, what are the basics of what came in these trucks & what works & what doesn't in them? Am I barking up the wrong tree thinking big block power is going to improve one of these? Can't find much info online, been searching 1/2 the evening.