Is that mech a ACMR or slide mech? If ACMR there were price arms under pull knob that got loose and out of place. Make sure lock out paws are working freely, when gummed up they move to slow to get out of the way.
Any 110V single price changer should work. Those old elctro-mech changers are easy to work on. Why not try fixing it first. Make sure it is the changer thats bad and not something in the machine jammed. What are the symtems?