What are the differences between c10, c20 and c30 frames?

[SWAG]

...and also are there frame differences between C and K trucks?
Mostly I'm curious about frame size / frame thickness, pictures would be nice. I tried searching and couldn't find anything because there were way too many threads.

Also can a 1/2 ton frame safely handle 3/4 ton loads? I have hauled 6200 lbs / 300 lbs tongue with another 300 lbs in the bed with my C10 over the mountains with no anti-sway bar, she was nearly bottomed out but I didn't have any trouble.