The 904 had the help of a torque convertor to get the car moving, The manual had the same 3 speeds that the auto had but had a deeper 1st. Your 904 can be repaired easily and can benefit from a huge selection of 'stall' convertors to get the old girl up and moving at a higher RPM. Auto to manual is a large job, with the trans being about half the total price, all the other bits add up fast. Welcome aboard!