I know on my 70 RoadRunner/Superbird chassis The original chassis shop wanted to place the main hoop Back far enough to weld the 4-link brackets too. But because of the wheel base, this would mean I either moved the rear wheels forward 10" or I drive from the back seat.



So instead he had to build it more like a ProStock truck, with the rear suspension mounts on an extended frame. This move the main hoop forward enough I could use a "figure c" style funny car cage which permits the drivers head to be partially under the main hoop.









Here is a pic (figure A style) with driver head in front of hoop, but with the suspension moved back for longer wheelbase car.








An A or E body car can have the suspension on braces in the main hoop area (sorry Camaro pic was only reference I could find - Pretend its a Cuda)







I HIGHLY doubt you can get a "nice" 25.3 cage for a B-body completely pre-bent. I would think you would need some type of tubing bender for at least a few places to insure a proper fit.

For the record, I second the nomination for have RJ Racecars build your chassis. I went with "a friend" and got screwed. For $9000 (2-1/2 years later)I got back a chassis that won't certify and has none of the welds done on the bottom. I will NEVER take anything back to "Cartel llc." For about the same money I could have have RJ or Adkins racecars build me a top sportsman chassis.