You have to be careful not to take too much if you go to the next size. How big is it? We have helicoils here at the shop well over 1-1/2" Problem is helicoils remove material as well and will weaken the rod.
There could be an issue with the plating getting too hot since it is an internal thread. A new chrome rod is probably around $100. It would need machined and to have the rod end cut off the old and welded on the new, but not a big deal. Other thing that could be done is to thread a stud in it, weld around the base of the stud plus a plug weld if you have room and use a nut to fasten the piston on.