The SS4705 Selenoid is becoming as rare as hen's teeth. I am assuming you have the MAX4050 Starter.
I know of a man here in N.C. (Generator Starter repairman - retired) that tested my extra starter. Last year I was lucky and still able to obtain and restore a MAX4050 should I ever need one for my spare parts. It still proved to be around $290 to do this, me doing all the work - replacing brushes, bushings, selenoid etc. I started with an ebay starter around $125 the rebuild kit from Bernbaum $40- ish a new SS4705 Selenoid from a man in Georgia around $125. Mind you others wanted $200 for that Selenoid ( out in California).
One like him should you remove it from the car can ascertain whether it is faulty in the actual Starter or the Selenoid. Then finally test it and check the proper Pinion Clearance which if memory serves me correctly it will be 1/16". Good Luck. I tried my friends and members of the Chrysler Club, whom all seem to be sitting on any decent spare starter parts available. I was truly fortunate enough to pull it together and restore one. I am not at will to part with it any time soon. The big Part Yards out west are your best bet. Can someone chime in with their names? D.V.A.P. and some to the North in Wisconsin, or Minnessota.
Tom