rear mounted cranes put a lot of stress on the overhang ,and a Bedford with a tapered rail would need considerable reinforcement......Even bogie drives with heavy section all the way need something like 3 layers of reinforcement.......On a single drive ,behind the cab is where I would want a crane.
About the time Noah was transporting animals I worked for International.
We did a fair bit of chassis alterations, always straight cuts BUT we had a weld procedure/pattern to run something like 5 welds per side.
This was to prevent distortion of the rails but also slowed the heat input into the rails.
Acco's were easy, just tack on the end, D Lines you had to let a section into the middle so double welds.
Cannot see a problem with the angle cut.