Re: 33 Chassis
Alfa actually continued to develop and stiffen the 33 shell until it ceased production. I was advised by a race car builder to try and get a '93 shell.
Most roll cages fit within the habaticle (ie where the seats and passengers are), so the suspension pick ups and across the struts are not always braced due to various regs hence a weak shell will still flex.
Plus, most Sud racers are ti's hence 2 door and the 33's are all 4 door, and believe it or not, a 4 door shell is generally stiffer than a 2 door.