I may be wrong, but I think the "curved piece" you are referring to actually connects to the accelerator peddle with a pin that passes through the hole you see and is held in place by a cotter pin. The other end should have a 90 degree bend in it that goes through the top hole of the bellcrank and is held by a washer and cotter pin. However, because you have a later engine than the cab/chassis, other modifications of the linkage may be required to make it work smoothly.
