I have seen rollbars on trucks and was wondering if it's required to run tubing from the inside of the cab via the back window into the bed for supports?
95 GMC C1500 Extended Cab Short Bed 6.5L Compound Turbo Diesel - /DT /B
My extended cab has no bars through the back window. The bars go where the back seats used to be. It is both SCTA/NHRA certified. Most extended cab trucks (all?) are done this way, not just me.
In any case, if you have full sized factory frame truck, the back bar angle should be tight for maximum strength due to the way a pickup frame is built. Ones that are at 45 deg do little. It's the frame in the rear that limits the impact angle, and it's not going to bend like a .125" thick small dia tube will. A tight angle back bar will support the main hoop, a highly angled bar has less than 1/2 the strength. It might even increase the risk due to frame flex, which is built into pickups. Over time, high angle bars will put constant load on the main hoop joints, like bending a wire back and forth.
Full sized pickups are stronger in the rear due to towing and bed load requirements. Cars are often the other way around. If anything front bars on a pickup make more sense, but are not practical.
As far as regular cabs go? I'll stay out of that. Look at the frame, where the hoops are, where the triangles are, and where the impact angle is and come to your own conclusions.