"The 240 is a slightly different kettle of fish with the Strut front suspension. Caster is technically not adjustable so perhaps Volvo had alternate lower control arms with less 'designed in' caster to reduce steering effort. I have never driven a 240 without power steering and wasn't aware that they were produced."
The 240 without power steering uses a different ball joint to change the castor.
A Chilean friend converted his 220 to Electric Power Assist Steering using a Saturn Vue EPAS unit and a controller sold by Bruno Lopez Antunes, of Portugal. He is pleased.
https://www.youtube.com/watch?v=S4S5kW9xcj8