67-72 Frame Question

[DBear]

Howdy All,
Looking for some clarification on the 67-72 frames. I do know that all 4x4 frames have straight rails in the rear, correct? On the 2wd frames, it seems that the frame curve outwards near the rear axle, and then kick back to straight after the rear axle? Is this the case with coil spring rear suspension and leaf spring suspension? I am also not sure if 2wd c10 trucks were available with leaf spring suspension, for I have never owned a 2wd c10? Thank you for any help you can provide.